Dentition of Pulmonate Mollusks. 125 



tant, delicate, oblique ribs, serrating either margin, those of the 

 upper centre meeting or ending before reaching the lower 

 margin. 



Lingual dentition quite peculiar. As Messrs. Crosse and Fis- 

 cher, in their exhaustive paper (Journ. de Conch.. XVIII, Jan., 

 1870), have indicated the different types of dentition found in 

 the genus, I have referred to their respective groups the various 

 species I have examined. 



Group A. — Two lateral teeth on each side of the median line; 

 marginals of a different form, varying in number. 



Cylindrella (Casta) Chemnitziana, Fer. Jamaica. 

 There are 10-1-10 teeth; two laterals on each side. 



Cylindrella cyclostoma, Pfr. (Trachella.) Lomas de Camoa, 

 Cuba. Mr. Arango. 



Jaw with over 70 ribs. 



LiDgual membrane with 10-1-10 teeth, two being laterals on either side; 

 the first marginal is a modification of the laterals, other marginals of usual 

 long and narrow shape, upper margin reflected. 



Cylindrella Humboldt i an a, Pfr. Cuba. Mr. Arango. 



Jaw with over 100 ribs. 



Lingual membrane with 8-1-8 teeth, as in C. rosea, figured by Crosse and 

 Fischer. The species belongs to their group Ihaumasla. 



Cylindrella rosea, Pfr. (Urocoptis.) 

 Jaw photographed in Am. Journ. Conch., V, p. 37. 



Cylindrella subula, Fer. {Mychostoma.) Jamaica. Mr. H. 

 Vend rev es. 



Lingual membrane with 10-1-10 teeth, as in C. yracUis, figured by Crosse 

 and Fischer. Lower margin of base of attachment of laterals delicately 

 fringed or crimped; marginals 8, long, laminar, with irregularly recurved 

 apices. 



Cylindrella scminuda, Ad. {Myrhostnma.) Jamaica, Mr. 

 G.loyne. 



Lingual membrane as in last species. 



Group C. — Lateral teeth more than two: marginal teeth simi- 

 lar to, and not to be distinguished from, the laterals. 



