GASTEROPODA. 115 



'base; mouth simple, terminal, and destitute of jaws; two 

 pectinated branchise projecting from the cavity ; mantle 

 large, protruding beyond the shell. Shell shield-shaped, 

 conically depressed ; concave within ; the vertex perforated ; 

 destitute of a spire. 



Fissurella Grceca. — The Greek Fissurella. Plate 

 XIV. fig. 20. Ovate-oblong, convex; the vertex with an 

 ovate perforation; strice cancellated and elevated, and the 

 sections tuberculated ; opening oblong- ovate, white or 

 bluish ; outside yellowish-brown, sometimes clouded. Half 

 an inch long. Inhabits the European seas. 



Genus 19.— SIPHO.— ^roM;n. 



Generic Character. — Animal unknown. Shell subconic, 

 vertex turned to one side, slightly spiral, with a small fis- 

 sure near the apex ; inside having a rhombic funnel-shaped 

 siphon, corresponding with the external fissure ; ovate. 



Sipho striatus. — The Striated Sipho. Plate XIV. 

 fig. 21. White, with strong divergent striae and faintly 

 striated concentrically ; margin slightly crenulated ; the 

 fissure triangular. Three-eighths of an inch long. Inhabits 

 the sea at Greenock. 



This is the Fissurella Noachina of Souerby and Lyell; Patella 

 Noachina of Linnteus. 



Genus 20.— EM AUGmULk.— Lamarck. 



Generic Character. — Body creeping; having two conical 

 tentacula, with the eyes placed at their external base ; 

 mantle very large, partly covering the margin of the shell 

 by its replicate borders; foot broad and very thick. Shell 

 conical, shield-shaped; vertex inclined to one side; internal 

 cavity simple ; the dorsal margin with a fissure. 



Emarginula fissura. — The Slit Emarginula. Plate 

 XIV. fig. 17. Oval, with reticulated striae, and ribs radiat- 

 ing from the vertex, which is obtuse and slightly recurved; 

 margin with a fissure, which extends nearly half-way to the 

 vertex; inside glossy white. Three-eighths of an inch 



