32 Dft JOHNSTON'S DESCRIPTIVE CATALOGUE OF THE 



Zool. Dan. ii. p. 41, pi. 71, fig. 10-12. B. pectinata, Dillw. 

 Rec. Sh. 481. Wood, Ind. Test. pi. 18, fig. 21. 



Hab. Found in shell-sand, and almost always imperfect, from having the 

 pectinated series of spines at the base rubbed off. Mr Alder has 

 found it entire in the stomach of a haddock. MuUer procured his 

 specimen from the stomach of a flounder. 



This shell, well described and figured by Muller, is larger than Bulla ca- 

 tena, and not so broad in proportion to the length ; the aperture is 

 less patulous, and the spire more complete. The clear spots or beads 

 of the transverse lines are much larger, oval, and, though often in ap- 

 parent contact, they are yet separate from one another, and not linked. 

 When recent it appears to be of a yellowish colour. 



" Muller and Chemnitz, in the same year, described two very different 

 shells with the name of B. scabra, and as neither has the preference 

 on the score of priority, I have changed the name of the present spe- 

 cies, because it offers another which is peculiarly applicable." — 

 Dillwpi. 



24. DiAPHANA. Thos. Brown. 



Obs. — This genus is indicated by Captain Thomas Brown in his 

 ** Illustrations of the Conchology of Great Britain and Ireland," 

 Edin. 1827 ; but I am not aware that he has anywhere given a defi- 

 nition of it. This is, perhaps, fortunate, for the name, being a com- 

 parative and an adjective one, is peculiarly objectionable. I adopt it 

 provisionally, because to do otherwise would necessitate the reduction 

 of Brown's names to synonymes, and might add to an overburdened no- 

 menclature; for, as the animals of the shells are unknown, we want 

 the grounds for referring them to their true genus. They will proba- 

 bly prove to be members of the genus Akera of Muller. 



1. Z>. pellucida, shell ovato-ventricose, pellucid, clear- white, smooth, 

 the apex truncate, flat, spiral but not umbilicate ; aperture the 

 length of the shell, entire, contracted above, widening below, the 

 pillar with a thin fold and a minute perforation behind it ; outer 

 lip thin and even. Length y^o^^' ^^^^ breadth about a third less. 

 Brown, Illust. pi. 38. fig. 10, 11. 



Jlab, In shell-sand. 



The shell, when large and full grown, is milk-white, but smaller speci- 

 mens are perfectly diaphanous, exhibiting the axis or columella very 

 clearly. The wide part of the apertui-e occupies about three-fourths 

 of its whole length, and the back of the shell is a little humped. It 

 seems to be identical with a shell figured by Muller in Zool. Dan. tub. 

 71, fig. 6 — 9, and described as very like the Akera bullata. 



2. D. Candida, shell ovato-globose, milk-white, pellucid, smooth ; 

 the spire small, very slightly raised, obtuse, of two whorls ; aper- 

 ture longer than wide, entire, the pillar arcuate, with a narrow 



