CLASSIFICATION. 75 



real line of demarcation can be traced ; the characters represent simply 

 the high tide of an osculation, which at its ebb merges into the next 

 incoming wave. 



Synopsis of Genera. 



PURPURA. Shell oblong-oval, last whorl large ; spire generally short ; 

 aperture ovate large, terminating in a very short, oblique channel, or 

 notched ; columella flattened ; outer lip simple. 



PURPUROIDEA. Shell turriculated, ventricose ; summit of the spire 

 sharp ; whorls convex, with a line of spines or tubercles on the 

 shoulder ; columella smooth, rounded, excavated in front; siphonal notch 

 wide ; outer lip thin. Fossil. 



LYSIS Gabb, Stomatiform, very oblique ; spire moderate ; whorls 

 costate ; aperture narrow, outer lip simple inner lip straight, concavely 

 expanded over the wide umbilicus so as to completely cover it. Fossil. 



IOPAS. Shell ovate, rugose, last whorl large ; spire acuminate ; aperture 

 moderate, emarginate and channelled in front ; columellar lip covered 

 witli a thin enamel, and with a prominent plait-like callosity at the hind 

 part ; outer lip sinuous, crenate within. 



VEXILLA. Shell purpuriform ; inner lip flattened and depressed, but 

 outer lip, when adult, thickened, inflected and toothed ; aperture wide. 



RICINULA. Shell ovate, solid ; spire short, whorls tubercular or spinous ; 

 aperture linear, narrow, contracted by callous projections, with a 

 short, oblique, emarginate canal in front ; inner lip tubercularly 

 wrinkled ; outer lip internally with plait-like teeth, often digitate. 



MONOCEROS. Shell ovate, last whorl large; spire rather elevated; 

 aperture semilunar ; inner lip wide and flattened ; outer lip crenated, 

 with a prominent tooth at the fore part. 



PSEUDOLIVA. Shell ovate, solid, subglobose ; spire very short, suture 

 slightly channeled, whorls tumid round the upper part ; aperture oval, 

 canal very short ; inner lip arcuated, with a callosity at the hind part ; 

 outer lip thin, furnished at the fore part with a small tooth or callosity. 



CHORUS. Shell laminately varicose, spinose on the shoulder ; canal 

 rather long ; outer lip with a spine as in Monoceros. 



PIKAXIA. Shell conical ; spire short, acute ; aperture oval-oblong, 

 emarginate anteriorly ; inner lip flattened, with several transverse plaits 

 in the middle ; outer lip acute, grooved internally. 



CONCHOLEPAS. Shell ovate, last whorl very large, expanded ; spire 

 very short, obliquely inclined towards the left side ; aperture very wide, 

 slightly channeled anteriorly ; inner lip flattened ; outer lip with two 

 small teeth in front. 



