GASTROPODA. [Aspidobranchia. 



Fam. SCISSURELLID^I, Pilsbry. 



Animal with a rather long rostrum, long ciliated tentacles, the eyes 

 at their outer bases ; foot rather narrow ; epipodium bearing 4 ciliated 

 cirri on each side. Radula with 1 central and 5 lateral teeth with 

 large expanded basal plates and finely denticulate recurved cusps, 

 the outer laterals hooked ; uncini numerous, narrow, with serrate 

 cusps. 



Shell minute, unicoloured, umbilicated, turbinate or depressed, 

 few-whorled, thin, with a thin layer of pearl inside ; aperture oval, 

 outer superior lip with a foramen or slit, and with a differently sculp- 

 tured band or anal fasciole encircling the whorls. Operculum circular, 

 corneous, thin, multispiral, with central nucleus. 



The foramen or slit corresponds to the end of the rectum, and 

 serves for the expulsion of the faces. 



The fossil (Tertiary) species number about as many as the Recent. 

 A group of very small shells, most of them living in deep water, and 

 widely distributed. The shell has a considerable resemblance to that 

 of Pleurotomaria, but the dentition and external anatomy of the 

 animal is decidedly nearer Trochidce. 



KEY TO GENERA. 



a. Shell with an open anal slit . . . . . . . . SCISSURELLA. 



b. Anal fissure closed, forming a foramen . . . . . . SCHISMOPE. 







Genus 1. SCISSURELLA, A. d'Orbigny, 1823. 



Scissurella, d'Orb., Mem. Soo. Hist, Nat. Paris, i, 1823, 340. Type : 5. 

 Itevigata, d'Orb. Anatomus, Ad., G.R.M., i, 439; not of Montfort, 1810. 

 Schizotrochus, Monterosato, Nom. Gen. e Spec., 1884, 39. Scissttrella, 

 Fischer, Man. de Conch., 846 ; Man. Conch. (1), xii, 49. 



Shell with an open anal slit, extending backward from the peri- 

 stome ; slit fasciole extending nearly to the apex. Slit fasciole edged 

 on either side by an upturned rim ; spiral sculpture is always present. 

 The animal is active. 



From Tertiary to Recent. 



Vernacular Name. Slit-shell. 



KEY TO SPECIES. 



a. Shell turbinate, strongly keeled, surface decussate . . . . Mantelli. 



b. Shell auriform, with spiral threads . . . . . . . . rosea. 



1. Scissurella Mantelli, Woodward, 1859. Plate 6, fig. 10. 



Scissurella Mantelli, Woodward, P.Z.S., 1859, 202, pi. 46, f. 8; Button, 

 M.N.Z.M., 103 ; Man. Conch. (1). xii, 54, pi. 57, f. 12. 



Shell small, turbinate. Spiral sculpture formed by a strong double 

 keel at the periphery, enclosing the anal fasciole ; above and below 

 it numerous close spiral striae, more distinct on the base ; there are 



