Occasional Papers of the Museum of Zoology 57 



M. Almost discoid in shape: 4; 62; 4. honiii (Gabb) 



MM. More elevated spire: 4.5; 78; 5. impiira (Pfr.) 



LL. Entire shell with beaded appearance, a few of the radial 

 folds may be developed into higher riblets. 

 N. Shell larger and more depressed. 

 O. 3; 83; 4 (type Microconus). wilhclmi (Pfr.) 



00. 3.4; 70; 4J/2. cockerellac Pilsbry 



NN. Shell small; Pupisoma-like ; texture like "fine woven 

 material." 1.95; 100; 4^. textilis Pilsbry 



HH. Apical whorls without definite spiral striations, but with regu- 

 larly spaced, smooth, well-dc'cloped riblets, parallel to growth- 

 lines. 



P. Larger species ; slight tendency towards spiral stri- 

 ations. 3; 60; 3^. tatei Pilsbry (blakeana Tate) 

 PP. Small species ; minute striations between ribs, 

 which form oblique squares, 4 microns across. 

 1-3; 48; 3/4- pilsbryi n. sp. 



Avercllia {TricJwdiscina) coactiliata (Ferussac) (1838). — 

 Seven specimens ; from leaves and bark of trees in lowland 

 jungle (H, I, b). One of these specimens contained the dried 

 remains of the animal, and from it the jaw and radula were 

 obtained. 



The arcuate jaw (fig. 9) bears 13 broad, low ribs, but is 

 also striate so that the ribs appear rather irregular and indis- 

 tinct. The radular formula (fig. 7) is: 



I 9 17 4 I 



C ;L — ;M — H h— ;or3i-i-3i. 



1-3 I 34-51 



The central and the inner nine laterals are functionally uni- 

 cuspid, but the rather long and slender mesocone bears lateral 

 expansions or wings on both sides, below the level of its cut- 

 ting edge. In soine of the centrals, each of these expansions 

 has a rather blunt and very indistinct cusp, which is only vis- 

 ible under the oil-immersion objective. (On other centrals I 

 was unable to detect these, and suspect that they are not always 



