224 PROCEEDINGS OF THE ACADEMY OF 
outer margin of the membrane ; both of the cusps bear distinct 
cutting points, the outer one smali, the inner one narrow, blunt, 
almost as long as the base of attachment. There are no distinct 
marginals, the laterals decreasing in size as they pass off laterally, 
those at the edge of the membrane (fig. ¢) having one large inner 
cutting point, and several, outer, irregular smaller ones. I have 
given @ a group of centrals and laterals, 6 a group of laterals, and 
e¢ an extreme lateral or marginal.’ 
I have had no opportunity of examining M. Kienert. 
Genus BULIMULUS, Leach.’ 
Jaw thin, arcuate, ends but little attenuated ; no median pro- 
jection to the cutting edge; anterior surface with numerous, 
separated, delicate ribs, denticulating either margin, 
sometimes the upper median ones running obliquely 
towards the median line, or even arranged en chevron 
as in Maeroceramus, with an upper median triangu- 
lar compartment. 
Oe i The jaw of B. dealbatus is here figured. It is quite 
dealbatus. arched. That of B. Marielinus and alternatus is of 
the same type. Ihave given on plate XVI., fig. 12, 
a more enlarged view of one end of the jaw of B. sufflatus, to 
show more accurately the character of the ribs. 
The lingual membrane of the genus as now received varies too 
much to aliow of a general description. It can only be said that 
the marginal teeth are quadrate, not aculeate. I will here simply 
confine myself to describing the membrane of the only one of our 
species of which I have preserved the lingual membrane. . 
Fig. 67 shows the general arrangement of the teeth on the mem- 
brane of B. dealbatus, the characters of the individual teeth being 
shown in pl. XV., fig. 7. There are 94 rows of 25—1—25 in one 
specimen examined. Another had 20—1—20 teeth, with 14 per- 
fect laterals. 
The central tooth has a base of attachment longer than wide, 
with but little expanded lower lateral angles, its lower margin 
Jaw of 
1 Similar dentition is found in M. turrieula, Pfr., of Cuba. See below, 
pl. XX., fig. 9. 
2T use this generic name only temporarily. As suggested by von 
Martens, it must eventually be restricted to those species whose dentition is 
like that of B. Guadelupensis, the type of the genus. 
