100 GASTROPODA. [Aspidobranchia. 



Length, 10 mm. ; breadth, 7 mm. ; height, 7 mm. (type). Length, 

 24mm.; breadth, 19mm.; height, llmm. (Chatham Islands). 

 Length, 22 mm. ; breadth, 15 mm. ; height, 13 mm. (Chatham 

 Islands). 



The animal is unknown. 



Type in the Mus. Hist. Nat., Paris. 



Hob. In fairly deep water. New Brighton, in roots of Macrocystis ; 

 Foveaux Strait, in 15 fathoms ; Port Pegasus, Stewart Island, in 

 18 fathoms (Captain Bollons) ; Snares and Bounty Islands, in 50 

 fathoms (Captain Bollons) ; Hauraki Gulf, in 25 fathoms ; Chatham 

 Islands ; Bay of Islands. 



Remarks. This species is variable in size and shape ; the largest 

 specimens I have seen are from the Chatham Islands, and they are 

 fairly solid. The examples from 50 fathoms are small and very thin. 



Fossil in the Miocene and Pliocene. 



Genus 3. SUBEMARGINULA, Blainville, 1825. 



Subemarginula, Blainville, Man. de Malacologie, 1825, 501. Type : Emar- 

 ginula emarginata, Bl. Subemarginula, Blainville, Man. Conch. (1), xii, 

 202, 273. Hemitoma, Swainson, Malac.. 356. Siphonella, Issel, Mai. 

 Mar. Rosso, 1869, 232. 



Mantle entire, not slit or tubular in front. 



Shell rounded-oval, conical, apex near the middle, curved back- 

 ward ; surface radiately ribbed ; anal notch generally short, con- 

 tinued upward as a groove inside, occupying the end of a slightly 

 prominent anterior rib, which is not sculptured differently from the 

 other ribs. The great muscle-scar exhibits a peculiarity diagnostic 

 of this genus : its anterior terminations are recurved and produced in- 

 ward toward the cavity of the apex. 



The genus is recorded from the Antilles, the Indo-Pacific, and 

 Australasia. 



KEY TO SPECIES. 



A. Shell with an internal anterior groove, area within the muscle- 



soar in the shape of a mushroom . . . . . . rugosa. 



B. Shell without an internal anterior groove, oblong, depressed, 



apex posterior. 



a. Shell without an anterior emargination, sides subparallel parmophoidea. 



b. Shell with a distinct emargination in front, sides nar- 



rowed in front . . . . . . . . . . intermedia. 



Sect. 1. CLYPIDINA, Gray, 1847. 



Clypidina, Gray, Syst. Dist. Moll. Brit. Mus., 164; A. Adams,' P.Z.S., 

 1851, 87. 



Internal groove distinct, ending in a short anterior notch ; area 

 within the muscle-scar decorated with a dark figure in the form of a 

 mushroom. 



