88 GIBBUS. 



G. MODIOLUS, Ferussac. PI. 21, figs. 97, 1. 



Profoundly rimate, rather thin, closely obliquely costulate ; 

 white ; lip shortly expanded, parietal tooth small. 



Length, 1 inch. 



Mauritius. 

 Var. MINOR (fig. 1). Length, 18 mill. 



G. MAURITIANUS, Morelet. PL 21, figs. 98, 3. 



Profoundly rimate, thin, corneous white, more or less diaph- 

 anous, thickly flexuously costulate, suture shortly toothed ; lip 

 somewhat thickened and a little expanded, parietal wall some- 

 times with a minute tooth. Length, 19-22 mill. 



Mauritius. 

 Var. MINOR (fig. 3). Length, 15 mill. 



Closely allied to G. modiolus, but appears to be thinner, more 

 finely and regularly striate, whorls a little more convex, the last 

 one less developed, aperture more perpendicular, parietal cal- 

 losity thinner, parietal tooth generally wanting. These differ- 

 ences should probably be considered varietal rather than specific. 



G. MONDRAINI, H. Adams. PI. 21, fig. 99. 



Profoundly arcuately rimate, very obliquely flexuously cos- 

 tate ; dirty yellowish ; aperture with a parietal tooth near the 

 lip; lip somewhat thickened, expanded and a little reflected, 

 subsinuous in the middle. Length, 20 mill. 



Mauritius. 

 G. BARCLAYI, H. Adams. PI. 21, fig. 4. 



Profoundly rimate, obliquely costulate, suture distinct, sub- 

 marginate ; lip almost continuous, thickened, expanded, subre- 

 flected, parietal tooth small ; epidermis straw-yellow. 



Length, 17 mill. 



Mauritius. 



Dr. von Martens suspects that this is identical with the next 

 species; judging from the figures, however, there is about the 

 usual amount of distinction between species in this group. 



G. FARINOSUS, Troschel. PI. 21, fig. 5. 



Rimate, opaque, white ; arcuately remotely obliquely costate ; 

 lip simple, subreflected, the margins joined by a shining callus, 

 parietal tooth moderate. < Length, 14 mill. 



Hab. unknown. 



