1882.] 'lightning' and 'porcupine' expeditions. 661 



shaped, or conical with a triangular lobe on each side ; these lobes 

 6eem to serve as flaps or wings to aid the locomotion of the animal, 

 and are expanded or contracted accordingly : captacula very nume- 

 rous (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 \3 

 somewhat like that of Crenella or Modiolaria. 



I admit that my 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 Mr. M'^Andrew'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 18/0, as J), 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 B. rubescens. 

 My 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 TEREs', Jeffreys. (Plate XLIX. fig. 5.) 



Shell cylindrical, gradually tapering to the basal point or pos- 

 terior extremity, gently curved, thin, glossy, and semitransparent ; 

 sculpture, none sxcept fine and numerous lines of growth : colour 

 whitish : mouth circular : base slightly but distinctly notched above 

 and below. L. 035, 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 \nS. teres, instead of being 

 bilateral as in that shell. 



/^y^*' 2. SiPHODENTALIUM AFFINE, M. SarS. 



Siphonodentalium affine, M. Sars, Christ. Vid. Selsk. Forh. 1864, 

 p. 299, t. vi. f. 34, 35. 



'Porcupine' Exp. 1869: St. 19, 28, 30. 1870: Atl. 3, 16, 

 )7, 17a. 



Distribution. Loffoden I., 100-300 fms. (M. 5'ars). 'Valorous* 

 Exp., 1450 fms. Nova Scotia, 35 fms. (Verrill)'! 



Not the young of S. vitreum (see B. C. v. p. 196), which in all 

 states of growth is more conical and not so cylindrical as (S. ajine ; 

 and the base or point is also different. The present species is not 

 half the size of (S. teres, and is much less slender and tapering. 



' Slendfir. 



