GASTEROPODA.. 155 



Distr., 100 sp. Brit., Norway, &c. World-wide. 



Fossil, above 100 sp. of patcUidse, including acmaa, L. siluriau — . N. 

 America, Europe. 



Sub-genera. Nacella, Schum. (=patina. Leach.) Example, P. pellucida. 

 PI. XL, fig. 23. Shell thin ; apex nearly marginal. Animal with the mouth 

 entire below. Branchiae not continued in front of the head. Found on the 

 fronds and stalks of sea-weeds. Brit., Cape, Cape Horn. 



Scutellina, Gray. S. crenidata. Shell with a broad margin, internally. 

 7 sp. Red Sea — Philippines — Pacific — Panama (Cmning). 



Metoptoma, PhiUips. M. pileus Ph. ShcU limpet-like, side beneath the 

 apex truncated. Resembling the posterior valve of a chiton. 7 sp. Carb. 

 limestone. Brit. 



AcMJCA, Eschscholtz. 



Etym., acme, a point. 



Sijn., tectm-a, M. Edw. Lottia and scm-ria. Gray. Patelioida, Quoy. 



Type, A. testudinalis. PI. XL, fig. 24. 



Shell like patella. Animal with a single pectinated gill ; lodged in a 

 cervical canty, and exserted fi-om the right side of the neck when the crea- 

 tm'e walks. Lingual teeth 3 on each side of the median line. Low-water to 

 30 fms. (Forbes.) 



Distr., 20 sp. Norway, Brit., Australia, Pacific, W. America. 



Snb -genera. Lepeta, Gray (= pro-pihdium, Forbes). Patella cseca, 

 Miill. Shell minute, apex posterior. Animal blind. Brit. 30 — 90 fms. 



Pilidiim, Forbes. P. fulva, MiiU. Brit. 20—80 fathoms water. Shell 

 small, apex anterior. Animal blind ; giUs 3, not projecting ; mantle even- 

 edged. Both lepeta and piHdimn have large single median teeth, with trilobed 

 hooks ; and 2 hooked uncini on each side. 



Gadinta (Adanson), Gray. 



Type, G. peruviana. Plate XL, fig. 26. Sy7i., mouretia, Sby. 

 Shell conical ; muscular impression horse-shoe shaped, the right side 

 shortest, terminating at the siphonal groove. 



Animal with a single cervical gill ; tentacles expanded, fmmel-shaped. 

 Distr., 8 sp. Medit., Red Sea, Africa, Peru. 

 Fossil, 1 sp. Sicily. 



? SiPHONAKiA, Blainville. 



Type, S. sipho. PI. XL, fig. 25. 



Shell like patella; apex sub- central, posterior; muscular impression 

 horse-shoe shaped, divided on the right side by a deep siphonal groove, which 

 produces a slight projection on the margin. 



