1902.] 



NATURAL SCIENCES OF PHILADELPHIA. 



523 



Surface ratlier finely striate 



r oostoma 



ydaetylopoma 



Surface coarselj' plicate : goniopoma 



'Lower palatal plica weak 

 or wanting. Palatal side 

 of the clausilium straight 

 distally, hardly excised, 

 columellar side not ex- 

 cised near the filament. 

 Lower palatal plica w^ell 

 developed. Palatal side 

 of the clausilium deeply 

 excised distally, the col- 

 umellar side excised near 

 the filament. 



The ^hape of the clausilium is shown on the plate. In C. oos- 

 toma it is not quite so strongly curved as in the other forms, there is 

 only a slight trace of the excavation on the palatal side of the 

 dLstal end, and there is no excision on the columellar side of the 

 filament. In daclylopoma there is a deep excision on the palatal 

 side of the distal end, which, however, passes gradually into the 

 broadly dilated palatal margin. The latter is but slightly thick- 

 ened. The columellar side is deeply emarginate or excised at the 

 origin of the filament. In goniopoma the deep distal excision ter- 

 minates somewhat abruptly at the end of a wide thickened rib 

 which strengthens the rest of the palatal margin. The excision 

 near the filament is slightly less deep than in daclylopoma. 



The excavation on the palatal side of the distal end of the clau- 

 silium when retracted fits over the lower palatal plica in all of these 

 forms. 



Section EUPII^DUSA Bttg. 



Euphcedusa is one of the most sharply defined of the numerous 

 sections into which Prof. Dr. Boettger divided the heterogeneous 

 group Ph(zdusa. At the time of the appearance of the classic 

 Claxmlienstadien but five Japanese species were known, placed by 

 Boettger in two groups typified by Chinese species. The number 

 of Japanese species has now been more than doubled, and requires 

 the arrangement proposed in my Catalogue, p. 654. This arrange- 

 ment was based upon the following characters : 

 I. — Superior lamella present. 



a. — Lunella perfect, Group of C. jos. 



b. — Lunt'lla incomplete or wanting, palatal plicic present. 



Group of C. shanghaiensis. 

 c. — Lunella and i)alatal plictc wanting. 



Group of C. subgibbera. 



