CHAP. IV. TYPES OP HARPULA. 119 



H. bullata, and a very near approach to it may be 

 traced in Harpula vexillum. We thus have three 

 resemblances ; one of which only we shall at present 

 regard. The numerous plaits of fulminata evince its 

 proximity to vexillum and Lapponica. To these succeed 

 the pre-eminently typical forms composed of Harpula 

 hebrcea, musica, polyzonalis, sulcata, &c., all of which 

 are thick, muricated, or spined. By these a passage is 

 formed to those slender-ribbed species where the two 

 last plaits are decidedly the thickest, and the upper ones 

 either very slender,, as in Harpula lyriformis*; or nearly 

 obsolete, as in Harpula costata^; or perfectly wanting, as 

 in Harpula nucleus. J In the apex of these shell s, how- 

 ever, here is a marked difference, plainly indicating a 

 gradation of structure: thus, in costata and multi- 

 costata , the apex, although obtuse, is not swelled, and 

 the volutions appear to be graduated equally, as in Har- 

 pula potyzonata. In nucleus, the apex seems almost 

 acute || ; but in H. lyriformis the second volution is 

 swelled and papillary : it is by this shell, therefore, 

 that we may pass to the next type of form, represented 

 by our Harpula bullata 1 ^, where the shell retains the 

 same shape as H. nucleus, and, like that, has only two 

 distinct plaits ; the whole shell is quite smooth ; 

 the spire is not only very obtuse, but the terminal volu- 

 tion is enlarged, even in the worn individual, which is the 

 only one we have yet seen; and its last turn is placed 

 on the side, not at the apex. For this form, however, 

 we have been prepared by the Harpula lyriformis, so 

 that we return again to the singular-shaped spine of 

 Harpula fulminata. Between H. bullata and H. ful- 



* tool. Journ. iii. pL 3. Zoo}. Illust, first series, pi. 54. 



t Brand's Journal, xvii. p. 33. 



$ Mawe's Conchology, frontisp. fig. 2. 



$ Broderip, in Zool. Journ. iii. pi. 3. fig. 2. 



|j I am not positive on this, not having a perfect example at this time 

 before me. 



f The only specimen I have yet seen of this shell is figured in Zool. IU. 

 2d series, pl.'lS. ; nor am I aware of any other, at least in the London cabi- 

 nets. Papillary spires are always remarkably thick ; and as it was evident 

 this specimen had been beaten and battered on the sea beach, it is highly 

 probable that the apex was originally much more thick and inflated than it 

 was on coming to my hands. It is now in the British Museum. 



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