1912.] 



NATURAL SCIENCES OF PHILADELPHIA. 



151 



PHENACOLEPAS MALONEI n. sp. 



BY E. G. VAN ATT A. 



Shell white, suborbicular. Apex moderately elevated, slightly 

 recurved, situated at the posterior fourth and to the right of the 

 median line. About 2 mm. from the smooth apex, fine raised radial 

 striae begin and increase in number to the margin where they number 

 about 150. The surface is covered with irregular concentric rows 

 of grains which become more regular near the margin, where they 

 form about 5 beaded costae completely encircling the shell. There 

 are 11 concentric linos of tubercles upon the posterior slope, 16 

 upon the right side, 22 upon the anterior slope and 17 upon the 

 left side. The posterior slope is nearly straight and slightly concave 

 near the apex, anterior slope convex, base slightly arcuate. Margin 



not crenulate. Interior with a slight pit under the apex; muscle 

 scar in the form of an irregular horseshoe, open in front, at which 

 point about 20 of the radial striae may be seen through the shell. 



Alt. 4.5, diam. 13.5, length 15 mm. 



In ballast from Santa Rosalia, L. California, collected by Mr. 

 J. G. Malone. Type No. 105,741 in the collection of the Academy 

 of Natural Sciences of Philadelphia. 



This shell differs from granulosa Thiele by having the apex nearer 

 the posterior margin, posterior slope shorter, anterior slope more 

 convex, and regular concentric costae near the margin. P. malonei 

 is more orbicular and larger than P. navicelloides Cpr. ; and is smaller 

 than P. mirabilis Sby. with finer sculpture and the apex nearer the 

 posterior margin. 



