100 BULLETIX 138, UNITED STATES NATIONAL MUSEUM 



Genus EUMORPHOCORYSTES von Binkhorst 



Eumorphocorystes von Binkhorst, Rheinlande u. Westphal. naturh. Verein, 

 Verb., vol. 14, 1857, p. 108 ; type, E. sciilptvs Binkhorst. 



Carapace very convex, egg-shaped, divided into two symmetrical 

 parts by a raised median line which ends anteriorly in a small point ; 

 one marginal tooth on either side placed well forward. Buccal cavity 

 elongated in a pointed arch and extending nearly half the length of 

 the carapace. Sternal surface not known. 



Cretaceous : Oligocene. 



EUMORPHOCORYSTES NASELENSIS, new species 

 Plate 24, figs. 9 and 10 



BescripH&H: — Carapace very convex in both directions but most 

 so from side to side, suggesting half an egg (pi. 24, fig. 10) ; widest 

 at lateral spine which is situated in advance of the anterior third; 

 postero-lateral margin rounding gradually into posterior margin 

 without an angle (pi. 24, fig. 9) ; antero-lateral margin becoming 

 concave soon after leaving the lateral spine and continuing to the 

 orbital angle, the outer spine directed inward. The anterior margin 

 in front view arches upward ; it appears to have three sinuses on tho 

 right side; the rostrum is not uncovered. A high blunt median 

 ridge the length of the carapace. The surface is covered with large, 

 unequal and adjacent punctae separated by a coarse network. Lat- 

 eral margin finely granulated. The lateral spine (pi. 24, fig. 10s) 

 seems to have pointed a little forward. 



Measurements. — Length of carapace (approximate) 53.6 mm.; 

 width behind lateral spine 39.3 mm. Distance from middle of base 

 of lateral spine (broken off at base) to outer angle of orbit 19 mm.; 

 distance from same point to middle of posterior margin 43.7 mm.; 

 width of front and orbits 16.2 mm.; greatest height of carapace 

 above lateral margin 13.2 mm. 



Occurrence. — Washington: Shale bluffs along Nasel River near 

 mouth of Sahnon Creek, Nasel; middle Oligocene (?) series. One 

 specimen showing little more than half of dorsal surface of cara- 

 pace. 



Relation. — This species has much in common with the preceding, 

 Ranidina tmUapensis : A similar outline and ornamentation, one 

 stout lateral spine, a narrow front and rear and a thick body. It 

 differs in having the dorsal surface much more convex, in the pres- 

 ence of a median ridge, in the lateral spine being nearer the front, 

 in the front narrower and the outer orbital spine inclined inward 

 instead of outward. 



