128 MALACOZOA. GASTEROPODA. PECTINIBRANCHIATA. 



stone, as well as by Mr. Lyell, under the name of Natica heli- 

 coides. At first sight it seems to have no resemblance to a 

 Natica, but rather to belong to the genus Bythinia or Paludina, 

 and Mr. Lyell has remarked that it closely resembles in shape 

 Paludina solida of Say ; but a comparison with various Naticae 

 has led to its being placed among them, and this arrangement 

 may be correct, although, as both Mr. Lyell and Dr. John- 

 stone observe, it departs from the normal form of the genus, 

 and the latter gentleman remarks that it is closely allied to the 

 Natica canaliculata of Gould. I had determined my specimen 

 to be identical with that described by the eminent naturalist 

 just mentioned, when I was favoured by Dr. Fleming with Mr. 

 Lyell's paper on the Fresh-water deposits of Eastern Norfolk, 

 in which is a figure of " Natica helicoides." On comparing it 

 with my specimen, I find no essential difference between them. 

 The spire being however a little shorter in mine, and the 

 mouth a little narrower at its anterior extremity, where there 

 is a slight angular appearance, as in all Naticae, but which has 

 not been represented in Mr. Lyell's figure. The only other 

 instance of its occurrence in a recent state is that mentioned by 

 Mr. Jeffreys, who found a specimen while dredging in Ler- 

 wick Sound. 



Natica helicoides. Johnst. Berw. Trans. 1835. p. 266. — Natica 

 helicoides. Lyell, Phil. Mag. S. 3. v. xvi. p. 365. f. 12. — Natica 

 helicoides. Jeffreys, in Ann. and Mag. of Nat. Hist. viii. 165. 



6. Natica squcdida. Dull-coloured Natica. 



Shell subglobose, thick ; of three-and-a-half very convex 

 turns, which are convex, separated by a subcanaliculate suture, 

 and striated transversely ; the spire depressed, convex, rather 

 obtuse ; the mouth nearly twice the length of the spire, oblique, 

 ovate, rather angulate anteriorly, the inner lip continued over 

 the columella, but very thin, and leaving a rather deep fissure 

 in the umbilical space, on wdiich there is no callosity ; the 

 colour yellowish-white. Length three-and-a-half twelfths, 

 breadth three-twelfths. 



A single specimen, dead, decayed, and having part of the 

 outer lip broken, was found by Miss Anne Macgillivray, in 

 October, 1812, among corallines brought up from deep water 

 off Aberdeen. It bears a great affinity to Natica helicoides, of 

 which it may possibly be merely a variety, should that shell 

 be found to vary as much in form as Bythinia tentaculata, 

 which it also somewhat resembles. The specimen however 



