Narrative of the surveying voyages of His Majesty's ships Adventure and Beagle Part 54

This sh.e.l.l was dredged up from 80 fathoms water in the offing of c.u.mberland Bay, at Juan Fernandez; it was attached to a branch of coral.

The hinge is broad and smooth, with distinct markings; the gape is rather wide, and the anterior part of the sh.e.l.l rises rather elegantly, like the stern of some Indian canoes, and in all the specimens but one, terminates in a point. The one above {549} described has a rounded form; the bows or front being rather elegantly and finely lamellated in a wavy form; the colour of the hinge is red, and the inside is generally of a brownish purple; in some it has a more yellow tinge.

13. ARCA PECTINOIDES.

_A. testa auriculata, cordata, ventricosa, multi-costata, transversim striata, alba, epidermide rufo nigricante, pilosa; umbonibus sub-approximatis, incurvatis, margine crenulato; long. 1; lat. 1-2/8; poll._

_Habitat ad_ Rio de Janeiro. _Mus. Brit., nost., Brod._

14. NUCULA STRIATA.

_N. testa striata, subtumida, cra.s.sa, sub-trigona, alba; latere antico productiori, sub-rostrato; long. 9/32; lat. 3/8; poll._

_Habitat in mari alto circa oras Patagonicas. Mus. nost._

Taken by a dredge in 40 fathoms water, 20 miles from the coast of South America, in the neighbourhood of Port Sta Elena.

15. MODIOLA SINUOSA.

_M. testa ventricosa, subovata, longitudinaliter striata; intus iridescente, margine sinuoso, epidermide fusca; long. 7/16; lat. 14/16 fere; poll._

_Habitat ad littora Brasiliae_ (Santos). _Mus. nost._

16. PECTEN PATACHONICUS.

_P. testa sub-aequivalvi, brunnea, longitudinaliter creberrime elevato-radiata; intus albida, longitudinaliter sub-radiata; long.

2-4/8; lat. 2-4/8; poll._

_Obs. auribus inaequalibus._

_Habitat in freto Magellanico pa.s.sim. Mus. nost._

17. PECTEN VITREUS.

_P. testa subaequivalvi, translucente, longitudinaliter multi-sulcata; sulcis convexis flavidulis, valva inferiore pallidiori; long. 1-9/16; lat. 1-4/8; poll._

_Obs. Auribus inaequalibus._

_Habitat in freto Magellanico pa.s.sim. Mus. nost._

This sh.e.l.l is found attached to the leaves of the _Fucus giganteus_, and, with other _Mollusca_, is the food of the Steamer or Race-horse Duck (_Micropterus brachypterus and M. Patachonicus_). {550}

18. TEREBRATULA FLEXUOSA.

_T. testa rotundato-cordata, gibba, sub-fusca, longitudinaliter creberrime sulcata; margine valde flexuoso; long. 1-3/8; lat. 1-4/8 paulo minus; poll._

_Habitat in freto Magellanico_ (Port Famine). _Mus. Brit., nost., Brod._

This sh.e.l.l, which was dredged up from deep water in the bay of Port Famine, attached to stones, is not a common sh.e.l.l in the Strait.

19. TEREBRATULA SOWERBII.

_T. testa subrotunda, planiuscula, subfusca, longitudinaliter radiatim transversim substriata, medio superne depressa, infra convexa, subglabra; margine utrinque crenulato, medio glabro; long. 1-7/16; lat.

7/16 paulo plus; alt. 11/16 poll._

_Habitat in freto Magellanico. Mus. nost., Geo. Sowerby._

20. CHITON SETIGER.

_C. testa ovali, antice subattenuata; valvis subdentatis, tenuiter concentrice striatis, antica 10-radiata, postica laevi, parvula; areis lateralibus striis duabus elevatis marginalibus; ligamento marginali laevigato, setigero; long. 2-3/8; lat. 1-3/8; poll._

_Habitat ad oras insulae_ Tierra del Fuego _et in freto Magellanico. Mus.

Brit., nost., Brod._

Sh.e.l.l ovate, rather attenuated towards the anterior end, generally of a light blue-green colour, variegated with markings of dark slate. Valves slightly beaked with minute concentric striae, the lateral compartments with two marginal ridges, which in some specimens are granulose, in others smooth. The anterior valve has eight, besides two marginal, ridges of the same character; the posterior valve is very small and smooth. Border coriaceous, and set with bristles produced from three rows of tufts or pores. In some of the specimens in my possession the bristles are rubbed off.

The sh.e.l.l is found in all parts of the sh.o.r.es of Tierra del Fuego, particularly on its seaward coast, and the western parts of the Strait of Magalhaens.

21. CHITON BOWENII.

_C. testa oblongo-ovata, castaneo-rufa; dorso elevato; valvis subdentatis, sublaevibus concentrice tenuiter striatis; areis lateralibus radiatim sulcatis; ligamento marginali granuloso, nigro; long. 3-2/8; lat. 1; poll._

{551}

_Habitat ad oras insulae_ Tierra del Fuego _et in freto Magellanico. Mus.

Brit., nost., Brod._

Sh.e.l.l oblong-ovate, and generally of a chestnut red, and the granulose ligament black; the colour of the younger specimens is more brilliant, and sometimes interspersed with yellow. Middle valves slightly toothed, and very delicately lineated, the lines forming an obtuse angle in the direction of the axis of the sh.e.l.l; the lateral compartments are marked with deeper striaea or grooves, radiating from the upper angle to the base, which, crossing the transverse markings of the valve, have a reticulated appearance: the anterior and posterior valves are radiated with fine lines.

This Chiton was discovered by Mr. Bowen, surgeon of the Beagle, by whom it was presented to me. The specimen was sent home among a collection of Natural History, transmitted in the year 1827.

22. FISSURELLA COARCTATA.

_F. testa ovata, antice attenuata, elevata; radiis frequentibus elevatis; interne virescenti; foraminis margine externo juxta medium coarctato, subdentato; long 2-5/16; lat. 1-13/16; alt. 14/16; poll._

_Habitat ad Portum_ Praya. _Mus. Brit., nost._

23. HELIX TRANSLUCENS.

_H. testa subglobosa, translucente, levissime transversim striata; anfractu basali linea longitudinali castanea sub-media ornato; long.

17/32; lat. 9/16; poll._

_Habitat ad_ Rio de Janeiro. _Mus. Brit., nost., Brod._

24. HELIX PUSIO.

_H. testa rotundo-complanata, creberrime striata, translucente, maculis castaneo-rufis ornata; long. 1/16; lat. 3/16; poll._