Fissuridea.] GASTROPODA. 105 



Surface cancellated by radiating and concentric riblets or striae. In- 

 ternal hole-callus truncated behind or having a pit there. Basal 

 edges of the shell in a plane or the sides slightly elevated ; ends never 

 elevated ; margin crenulated. 



Mediterranean, Atlantic, Indo-Pacific. 



Fossil in the Tertiary. 



The young Fissuridea has a recurved spiral apex with the fissure 

 in front of it, exactly as in Rimula. The truncation and pit back of 

 the hole-callus are homologous with the septum and pit back of the 

 hole in Puncturella. 



]. Fissuridea monilifera, Hutton, 1873. Plate 8, fig. 8. 



L/icapina monilifera, Hutt., C.M.M., 42. Fissurella monilifera, Hutt., P.L.S. 

 N.S.W., ix, 370. Megatebennus moniliferus, Hutt., Plioc. M., 72, pi. 8, 

 f. 76. Glyphis (?) monilifera, Hiitt., Man. Conch. (1), xii, 227. 



Shell small, oval, slightly wider behind the foramen, depressed 

 conoidal. Sculpture consisting of very numerous close and fine radiate 

 riblets, distinctly wavy, crossed by very fine close concentric threads, 

 nodulous at the points of intersection. Colour white, buff, or tawny. 

 Anterior slope straight or slightly convex, posterior slope straight or 

 lightly concave. Foramen keyhole-shaped, very little in front of the 

 middle, its plane nearly horizontal. Interior white, smooth, only 

 microscopically roughened, and with indistinct narrow radiate folds ; 

 foramen surrounded by a triangular strong white callus ; muscular 

 impression distinct. Margin smooth, sharp, sometimes finely denti- 

 culate. 



Length, 15-5 mm. ; breadth, 11-5 mm. ; height, 5mm. (type). 

 Length, 23 mm. ; breadth, 16 mm. ; height, 6 mm. (my largest speci- 

 men). 



Type in the Dominion Museum, Wellington. 



Hob. Stewart Island, in 15 fathoms (type) ; Port Pegasus, Stewart 

 Island, in 18 fathoms ; Snares, in 50 fathoms (Captain Bollons). 



Fossil in the Pliocene. 



Fam. TROCHID^l, d'Orbigny. 



Animal similar in general form to the Turbinidce. Visceral mass 

 and shell spirally coiled. Epipodial line bearing 1, several, or 

 many smooth or ciliated cirri on each side ; head with a short, broad 

 rostrum ; intertentacular lobes simple or digitated, separate or united 

 across the front, sometimes obsolete. A single ctenidium ; eyes open 

 Jaws developed or absent. 



Shell nacreous within, conical, pyramidal, subglobose, turbinate 

 or helicoid ; aperture entire, tetragonal or rounded ; persistome gene- 

 rally not continuous. Operculum circular, thin, entirely corneous, 

 formed of numerous gradually increasing whorls ; nucleus central. 



