1915.] NATURAL SCIENCES OF PHILADELPHIA. 27 



Semele regularis n. sp. 



Gulf of California, off La Paz, in 10 to 30 fathoms. (Coll. U. S. N. 

 Mils., No. 76,433.) 



This is a thin, delicate, usually pure white species of elliptical 

 outline, sculptured with low, obtuse, concentric lamellae, regularlj^ 

 disposed, with fine concentric lineation between them and no trace 

 of radial striation. The beaks are nearly central and the pallial 

 sinus is high, short, subcircular, and hardly extends behind the 

 vertical of the beaks. Some specimens have a faint orange flush 

 internally. The most perfect specimen measures 22 mm. long, 

 17 mm. high, and 6 mm. in diameter. The umbo is about 12 mm. 

 behind the anterior end. Fragments show that the shell grows at 

 least one half larger. 

 Semele pacifica n. sp. 



Catalina Island, California, to Acapulco, Mexico, in 9 to 21 fathoms. 

 (Coll. U. S. N. Mus., No. 211,728.) 



This is the shell usually referred to S. cancellata Sowerby, 1830 

 (S. hellastriata Conrad, 1837), but which differs from that Atlantic 

 species in its smaller lunule, shorter and weaker right lateral tooth, 

 and sharper and more delicate concentric sculpture. It is a rare 

 form and doubtless the two descend from the same Oligocene ances- 

 tors. 

 Semele incongrua Carpenter, 1863. 



Monterey, California, to the Coronado Islands, Lower California. 

 (Coll. U. S. N. Mus.) 



This is a well-defined species, and the Pliocene shell named S. 

 pulchra var. montereyi by Arnold, 1903, should be referred to it 

 rather than to pulchra as a variety. 



Semele pulchra Sowerby, 1832. 



Monterey, California, to Ecuador. (Coll. U. S. N. Mus.) 

 Semele venusta A. Adams, 1853. 



Acapulco, Mexico, to West Colombia, South America. (Coll. 

 U. S. N. Mus.) 



The S. ruhrolineata Conrad, 1837, San Diego, California, has not 

 been definitely recognized since it was originally described, and the 

 type is said to be lost. 



It has been, by a lapsus, referred to by Dr. Carpenter as S. ruhro- 

 tincta, and was surmised by him to be a variety of S. pulchra, but 

 the two have no resemblance to each other, judging by Conrad's 

 figure. There does not seem to be any good ground for doubting 



