252 PROCEEDINGS OF THE ACADEMY OF 
ranged as usual in the genus(see ante, p. 222). The base of attach- 
ment is shorter and stouter, the outer cusp of the laterals is larger 
and on a shorter and stouter pedicle than in Oylindrella SCHUM, 
figured on page 222. There are no distinct marginals, the teeth 
slightly and gradually changing in size as they pass off laterally, 
until in the extremes the two cutting points become of almost 
equal size and the outer one ceases to be on a distinct pedicle ; 
the base of attachment also in the extremes is almost square. 
This membrane is of interest, being the first described of the 
section Gongylostoma, whose dentition was unknown to Messrs. 
Crosse and Fischer. 
Cylindrella cyclostoma, Pfr. 
Mr. Arango to Mr. Bland. Lemas de Camoa, Cuba. 
Jaw as usual in the genus, with over 70 delicate ribs (see ante, 
p- 222). 
Lingual membrane long and narrow, as usual in the genus. 
Laterals 2, marginals about 8, these and centrals of same type as 
those figured by Messrs. Fischer and Crosse (Journal de Conchy- 
liologie, 2d s., X.), for the group Cylindrella, s.s.,as in Cylin- 
drella costata, pl. IV., fig. 2. 
The first marginal, however, surely is of same type as the late- 
rals, though much smaller and somewhat modified in form. It 
appears like a transition from the one to the other. 
Cylindrella (Thauwmasia) Humboldtiana, Pfr. 
Cuba. Mr. Arango to Mr. Bland. 
Lingual membrane long and narrow, as usual in the genus. 
Teeth 8--1—8 of same type as figured by Messrs. Fischer and 
Crosse for C. rosea (Journ. de Conch., X VIII, 1870, pl. IV. fig. 4). 
The species belongs, therefore, to their group Thaumasia. 
The jaw is as usual in the genus, with about 100 ribs. 
EXPLANATION OF THE PLATES. 
PATE XIX. 
t. Testicle. 
e. Hpididymis. 
ac. Accessory gland of last. 
ov. Ovary. 
ovid. Oviduct. 
