Laoiitu . 



GASTROPODA. 



747 



3. Group of Laoma Erigone. 



Umbilical perforation narrow or moderate, quite open, its diameter 

 one-sixth or less of the greatest diameter of the shell. 



Suture margined. 



KEY TO SPECIES. 



A. Upper surface of shell with radial riblets. 



a. Riblets ciliated at suture and periphery. 



b. Spire 3 times the height of the aperture . . 

 bb. Spire 1^ times the height of the aperture 

 aa. Periphery convex ; crisp riblets on upper surface 

 aaa. Periphery bluntly or distinctly angled. 

 b. Riblets serrate, interstices reticulated 

 bb. Riblets. simple. 



c. Last whorl only with riblets, 10 per millimetre ; 



spire 2J times the height of the aperture . . 



re. Whorls with fine close riblets, 50 per millimetre ; 



spire 1 times the height of the aperture . . 



ccc. Whorls with distant riblets, 5 per millimetre ; 



spire the same height as the aperture 



B. Upper surface of shell with more or less distinct growth-lines 



only. 

 a. 



b. Protoconch with microscopic spiral lines ; suture 



prominently margined, periphery keeled 

 bb. Protoconch smooth. 



c. Periphery subangled, suture faintly margined . . 

 cc. Periphery sharply angled ; perforation open, 



nearly one- fifth of diameter 

 ccc. Periphery acutely keeled ; perforation narrow, 



sometimes partly hidden 

 aa. Suture simple. 



1. Periphery perfectly convex. 



b. Only the protoconch has microscopic spiral lines ; 



spire lower than the aperture 



bb. Protoconch smooth, following whorls spirally 

 microscopically striate ; height of spire equal 

 to that of the aperture 

 Periphery but lightly angled. 

 b. Spire half the height of aperture ; perforation 



one-tenth of diameter 



bb. Height of spire a little less than that of the aper- 

 ture ; perforation one-sixth of diameter 

 Periphery distinctly angled or subcarinated. 

 b. Shell fulvous, no colour-markings ; dimensions, 



5 mm. by 2g mm. 

 bb. Shell with brown streaks. 



c. Microscopic spirals obsolete ; spire a little 



higher than the aperture 



cc. Microscopic spirals distinct ; height of spire 

 a little less than that of the aperture . . 

 4. Periphery keeled. 



b. Protoconch smooth ; spire a little higher than 

 the aperture ; dimensions, 3f mm. by 2i mm. 

 bb. Protoconch with microscopic spirals ; height of 

 spire equal to that of the aperture ; dimen- 

 sions, 4j mm. by 3 mm. . . 



2. 



3. 



regularis. 



spiralis. 

 Campbellica. 



lerratocoslata. 



tiriyone. 

 cognala. 

 Phrynia. 



marginata. 



Alfredi. 



Trailli. 



lniii..sitans. 



Hamiltoni. 

 niirruretint/rtia. 



compressa. 

 t/labriuscula. 



fatua. 



Hnasti. 

 Moellendorffi. 



C'elia. 

 liratvla. 



