1901.] NATURAL SCIENCES OF PHILADELPHIA. 629 



and especially in the clausiliurn, which is unusually straight and 

 not in the least oblique at the apex. 



Clausilia ptychocyma var. yakushimse Pilsbry. PI. XXXV, fig. 11. 



Pilsbry, I. c. 



Yaku-shima, Osumi. Types No. 81,934 Coll. A. K S. P., 

 from No. 6646 of Mr. Hirase's collection. 



Section TYRANNOPH^DUSA Pilsbry. 



Clausilium obliquely truncate distally, the columellar side of the 

 apex slanting, strongly thickened along the inner face. Shell 

 having the superior and spiral lamellae contiguous or separated, 

 the inferior lamella deeply receding, straight or obliquely ascend- 

 ing inside ; spiral and columellar lamella usually continued within 

 past the ventral side; lunella united to both upper and lower 

 palatal plicae or separated from the upper plica, usually latero- ventral 

 or ventral in position. Type C. mikado Pils. 



The characters of this section were only imperfectly perceived 

 when it was originally proposed last year. Further investigation 

 shows it to be quite distinct from Semiphcedusa (which resembles 

 it in the receding inferior lamella), by the oblique and thickened 

 end of the clausilium. Moreover, the lamellae extend further 

 inward, the closing apparatus retreats more deeply: there is often 

 a crest on the neck parallel to the outer lip, and in some species 

 the lip is plicate in the subcolumellar region, and there may be 

 interlamellar folds. 



The section includes three groups of species, distinguished as 

 follows : 



a. A strong crest behind the outer lip, Group of C. tanegashimce. 

 a 1 . No distinct crest. 



b. Lunella curving inward above (con crescent with the outer 

 end of the upper palatal plica), Group of C. bilabrata. 

 b l . Lunella straight ; together with the palatal plicae forming 

 an I -shaped barrier, or separated from the upper pala- 

 tal plica, Group of C. mikado. 



Group of C. bilabrata. 



Tyrannophaedusae of ordinary form, with the clausilium oblique 

 and thickened at the apex, excised on the columellar side of the fila- 

 ment. Superior and spiral lamellae separated or nearly so, the 

 spiral and inferior extending inward to or past the ventral side. 



