1892.] NATURAL SCIENCES OF PHILADELPHIA. 339 



Helicina ghiesbreghti Pfr. 



Mountains of Poana, Tabasco. 

 Helicina oweniana Pfr. var. 



A rather aberrant variety, but in all j^robability this species. 

 Poana, Tabasco. 



Helicina tenuis Pfr. var. chiapensis Pfr. 



Poana, Tabasco. 

 Tlnio semigranosus Busch. 



Rio Tulija, Tabasco. 

 Anodonta globosa Lea. 



A very large specimen, measuring 182x136x92 mill. 



San Juan Bautista, Tabasco. 



The splendid work of Crosse and Fisclier upon the genus Pachy- 

 cliihis enables me to readily classify the specimens collected by 

 Prof. Rovirosa; the illustrations of the varieties of P. glaphyrus 

 are especially valuable. 



Pachychilus glaphyrus Morelet. 



This species is an exceedingly variable one, more so perhaps than 

 any other Mexican Melanian. The American student, however, 

 will readily call to mind cases of equal variability among the species 

 of our Southern States. The material sent by Prof Rovirosa com- 

 prises a number of varietal forms not before made known. 



P. glaphyrus Rovirosai Pils. 



This was figured and described under the name P. (polygonaius 

 var.?) Rovirosaiin the Proceedings, 1892, jx 153, PL VIII, figs. 9, 10. 

 I was at that time not aware of the fact that Morelet's name glaph- 

 yrus antedated that given by Lea, polygonatus. This form is allied 

 to P. glaphyrus typical, and to the var. scamnata, but it is distinct 

 from both. The form is notable for its stout, straight-sided spire, 

 non-impressed sutures, and the unsculptured young. 

 P. glaphyrus var. Wween polygonatus and immanis. (PI. XIV, figs. 5, 6.) 



The two specimens figured are of the same size but differ in sculpt- 

 ure. One (fig. 6) is smooth above and below, having a strong sub- 

 spinous keel at the periphery, and a smooth, acute keel below it. 

 Upon the earlier whorls of the spire there are longitudinal waves, 

 and two spiral cords above the peripheral keel, which diminishes 

 in size. The base has no spirals. The other specimen has the 



