C(ECUM. 181 



" rounded in a larger one, in which those near the mouth 

 are largest, and the whole are crossed by obsolete longi- 

 tudinal ridges." 



This last appears to agree with the Brochus annulatus 

 and reiiculattis, Brown, Illust. Conch. Gr. B. pp. 124, 125, 

 pi. 56, f. 12 (adult) 11 (young). 



The genus Coecum has not been studied with that due 

 attention to its foreign members Avhich alone entitles us to 

 pronounce upon what are the permanent characters by 

 which its species are determinable. Hence we feel some 

 hesitation in regarding the present shell as distinct from 

 trachea, especially as we have seen but a single specimen. 

 (PI. LXXXVIII. fig. 7.) 



The individual alluded to was forwarded to us by Mr. 

 Alder as from the south coast of England, and bears a 

 marked general resemblance to the preceding shell. It is 

 evidently a dead example, hence its opacity and squalid 

 white hue are of no value as distinctions. The great pecu- 

 liarity consists in the annular ridges, being regularly and 

 distinctly, though very finely, costellated in a longitudinal 

 direction, the raised lines being partially, also, continued in 

 the interstitial furrows where the microscopic striula3 that 

 are so generally present in trachea are likewise here and 

 there perceptible. The first three annulations are strong 

 and projecting, but after them the ridges are so depressed 

 that their edges alone are elevated, so that they resemble 

 lamellffl. The clausum or posterior termination is almost 

 entirely concealed within the tube, and is very acute and 

 narrow, with its point adjacent to the arched side of the 

 shell. 



0. GLABRUxM, Montagu. 

 Very thin, pure white, smooth or nearly so. 



Plate LXIX., fig. 5. 



Dentalium nunuluin, Linn., ed. \'2, p. 12G4 (probably). — Dillw. Recent Shells, 

 vol. ii. p. 1068. 



