1902.] 



NATURAL SCIENCES OF PHILADELPHIA. 



523 



f oostoma 



Surface rather finely striate : 



L dactylopoma 



Surface coarsely 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 well 

 developed. Palatal side 

 of the clausilium deeply 

 excised distally, the col- 

 umellar side excised near 

 the filament. 



The shape 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 

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

 filament. In dadylopoma 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 rilament. 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 dactylopoma. 



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 EUPHJ3DUSA Bttg. 



Euphcedusa is one of the most sharply defined of the numerous 

 sections into which Prof. Dr. Boettger divided the heterogeneous 

 group Phczdusa. At the time of the appearance of the classic 

 Clausilienstudien 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. Lunell a perfect, Group of C. jos. 



b. Lunella incomplete or wanting, palatal plicae present, 



Group of C. shanghaiensis. 

 c. Lunella and palatal plicae wanting, 



Group of C. subgibbera. 



