MORPHOLOGY OF THE HELICINID.E. 763 



They were numbered respectively 16, 30, and 31. The first two I 

 have identified without diflSculty, the third appears to be new 

 to science, and I will give a diagnosis of it in the latter part of 

 this paper. I am indebted to Mi'. E. A. Smith for these and for 

 the two following species : — 



Orohophana pachystoma ponsonhyi Smith. Admiralty Islands. 

 Palceohelicina ida' Wagn. Amboina. 



In describing the anatomy it will be convenient to take Alcadia 

 as the type, and to note such diffei'ences as may exist between it 

 and the other genera at the end of the description of each system 

 of oi'gans. 



External Characters, Mantle, Mantle-cavity, 

 and Muscular System. 



Isenki'ahe (4) has given an account of these so sufiicient and 

 accurate that it is not necessary for me to do more than call 

 attention to some special features exhibited in fig. 1 (PI. XXX.), 

 which is a I'epresentation of a left side view of Alcadia palliata : 

 the mantle has been cut through on the left side close above the 

 columellar muscle, the cut has been extended back to nearly the 

 extreme hinder end of the mantle-cavity, and the mantle has been 

 turned over towards the right. As compared with the Xeritidse, 

 in this and in all the other species of Helicinidas that I havo 

 examined the foot is attached to the head and body by a longer 

 and narroweivpedicle, the opercular lobe is relatively smaller, the 

 snout is narrower and longer, the columellar muscles of greater 

 antero-posterior length, and the whole body is longer, giving the 

 appearance of an increase in the coiling of the visceral mass, but 

 this last feature is more apparent than real, as I shall show. 

 A glance at the figure shows that the increased length of the 

 body is chiefly due to the elongation of the post-tentacular region 

 and the part of the body immediately following. Using 

 Amaudrut's (1) phrases, we have an almost extreme case of 

 " allongement posttentacvilaire," followed by an " allongement 

 dorsal," and many of the peculiar features of helicinid anatomy 

 areto be explained by the excessive growth in length of these two 

 regions. The post-tentacular region lies above the anterior two- 

 thirds of the columellar muscle, and its posterior limit is max'ked 

 by two or three deep wrinkles of the body-wall. The body-wall 

 of this post-tentacular region is fairly stout and muscular, and 

 the epidermis is, as a rule, deeply pigmented. The colour differs 

 in different species. It is nearly black in Alcadia, grey shading 

 posteriorly into white in Eutrochatella pulchella, yellowish gi'ey 

 in Lucidella aureola, a dark chocolate-brown in Pala^ohelicina idee, 

 and a bright chestnut-brown in Aphanoconia gouldiana. In the 

 post-tentacular region are contained the buccal bulb and the 

 greater part of the oesophageal pouches. In the dorsal region 

 following on the post-tentacular the body-wall is thin and nearly 



