836 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxx. 



LEPTOPHOCA, new genus. 



An extinct phocine pinniped luannnal, liaving- the hiimeru!? more 

 slender than in any existing- genus of seals. Deltoid ridge well devel- 

 oped and broad at the upper, or proximal, end, but narrowing rap- 

 idly below and terminating in a thin edge, which, at a point 

 considerably below the middle of the bone, joins at an ol)tuse angle 

 the ridge running to the inner edge of the trochea. Lesser tuberosity 

 only moderately developed, the bicipital groove between it and the 

 greater tuberosity ver}' narrow relatively. Entepicondylar foramen 

 present. -Zy/>e o^ t1><? (/einis. — Leptophoea h-nl.^. 



LEPTOPHOCA LENIS, new species. 



Size, as determined from the humerus, about that of Phoca <ji'nn- 

 landlcd. (See Plate LXXV, lig. 1.) Least transverse diameter of 

 shaft of humerus less than one-seventh the length. Breadth from ente- 

 picondylar foramen to supinator ridge less than one-fourth the length. 

 Internal face of deltoid ridge plane. Root of the lesser tuberosity 

 not forming a strong ridge on the internal face of the shaft. 



Medfiurements of hHtnenis. — Total length, 129 mm.; least diameter 

 of shaft, transversely, IT; ditto^ antero-posteriorl}-, on exterior side, 

 27; diameter of shaft at insertion of head, posteriori v, 26; distance 

 from distal end of deltoid ridge to center of trochlea, 58; greatest 

 breadth on line of proximal margin of trochlea, anteriorh^ 38; breadth 

 from entepicondylar foramen to supinator ridge, posteriorly, 30; great- 

 est breadth of trochlea, anteriorly, 24; breadth of entepicondylar 

 foramen, 2.5. 



Type-s.peciiri€n. — No. 5359., U.S.N.M., Vertebrate Paleontology. 

 Humerus, from Calvei-t Cliffs, Calvert County, Maryland, between 

 Chesapeake Beach and l*lum Point. Collected ]»y F. W. True, June 

 20, 1905. Plate LXX\'. ligs. 2-4. 



LcptopJioca lenis was i)robabl3' about the size of Phoca (irnuldiidlai. 

 The humerus of the latter, while of almost exactly the same length, 

 is nuich thicker, tmd the deltoid ridge, as in all existing seals, is thick 

 distally as well as proximally. The les.ser tul)erosity is much more 

 massive than in Leptophoea and is separated from greatei' tuberosity 

 by a very wide bicipital groove. 



The genus Mouachus^ with which several genera of fossil s(>al^ have 

 been compared, differs in that the shaft is quite straight, the bicipital 

 groove wide, and the entepicondylar foramen absent. 



On account of Dr. J. A. Allen's careful analysis of the data relating 

 to supposed species of American fossil seals, described or mentioned 

 by Leidy and other paleontologists," it does not seem necessary to con- 

 sider them in detail in. this place. His conclusion, namely, that not a 



"J. A. AUi'ii, North Ainerican riiiiiipfd.s, 1880, pp. 469-476. 



