OCR Text |
Show 1882.] 'LIGHTNING' AND'PORCUPINE'EXPEDITIONS. 661 shaped, or conical with a triangular lobe on each side; these lobes seem to serve as flaps or wings to aid the locomotion of the animal, and are expanded or contracted accordingly : captacula very numerous (apparently from 50 to 100), cylindrical, slender, and extensile, each terminating in an oblong bulb : mantle forming a slight collar inside the mouth or front opening of the shell: gills or branchiae brown, arranged in two leaves: liver yellow, granular; the lower fourth of the shell is empty and not occupied by the animal. The captacula are always in active and incessant motion, even when the other parts of the animal are at rest. The action of the foot is somewhat like that of Crenella or Modiolaria. I admit that m y friend Dr. Fischer is right in giving this species the name imposed by Sowerby, although I do not agree with the latter in saying that M r . McAndrew's shell is the same as that from the Philippines. The latter species is larger and proportionally broader towards the front or anterior end, and is consequently less slender and thread-like; and it is also more curved. I would suggest for that species the name subrectum. I described the present species in the Ann. & Mag. N. H. for July 1870, as D. gracile ; but that name had been preoccupied by Prof. Meek for a North-American fossil. The colour of the shell is clear white; Sowerby described it as " pallide fulva." There is a terminal sheath as in D. rubescens. M y largest specimen is half an inch in length. It is more regularly cylindrical than the young of D. rubescens, narrower and nearly equal in breadth throughout. Very young specimens of the present species have a bulbous point like D. entalis and other species. 1. SIPHODENTALIUM TERES1, Jeffreys. (Plate XLIX. fig. 5.) S H E L L cylindrical, gradually tapering to the basal point or posterior extremity, gently curved, thin, glossy, and semitransparent; sculpture, none except fine and numerous lines of growth : colour whitish : mouth circular : base slightly but distinctly notched above and below. L. 0*35, B. 0*05. ' Porcupine' Exp. 1870, Atl. St. 16, 17, 17«. The position of the terminal notches in this species differs from that of the slits in Dischides, being placed one on the convex and the other on the concave end of the shell in 8. teres, instead of being bilateral as in that shell. 2. SIPHODENTALIUM AFFINE, M. Sars. Siphonodentalium ajflne, M. Sars, Christ. Vid. Selsk. Forh. p. 299, t. vi. f. 34, 35. 'Porcupine' Exp. 1869: St. 19, 28, 30. 1870: Atl. 3, 16, 17, 17a. Distribution. Loffoden I., 100-300 fms. (M. Sars). 'Valorous' Exp., 1450 fms. Nova Scotia, 35 fms. (Verrill)1 Not the young of 8. vitreum (see B. C. v. p. 196), which in all states of growth is more conical and not so cylindrical as S. ajflne; and the base or point is also different. The present species is not half the size of 8. teres, and is much less slender and tapering. 1 Slender. |