82 BULLETIN 138, LT]sriTED STATES NATIONAL MUSEUM 



face without forming a definite marginal line; on the outer surface 

 the granules almost disappear. 



Measurements. — Male, holotype, length of carapace from outer 

 angle of orbit 34.7 mm., chord of antero-lateral margin, from outer 

 angle of orbit to the interval behind the twelfth tooth (orbital tooth 

 not counted) 24.5 mm. 



Occurrence. — Oregon : Rocky Point, 4 miles east of Yaquina City ; 

 Oligocene series; one specimen, holotype, showing less than half the 

 carapace and a piece of the sternum with spine; in University of 

 California. 



Relation. — This species is closely allied to M. gaudichaudfi (Milne 

 Edwards)-'-* which inhabits the deeper waters of the Pacific coast 

 from the Farralon Islands to Chile at a depth of 26 to 218 fathoms. 

 The antero-lateral teeth are of the salne character and the ridges of 

 the carapace are similarly placed and have the same number of 

 tubercles. In gaudichaudU the two posterior tubercles of the inner 

 branchial ridge are nearer together, scarcely further apart than are 

 the two anterior tubercles of the same ridge. In gaudichaudU the 

 number of antero-lateral teeth varies from 13 to 15 ; our species may 

 have had as many, for the margin is broken away at the widest part 

 of the carapace. The granulation of carapace and sternum is more 

 uniform and more crowded in gaudichaAidii., and the merus of the 

 ambulatory legs more compressed. 



MURSIA MARCUSANA, new species 

 Plate 19, figs. 6 and 7 



Description. — Antero-lateral margin strongly arched (pi. 19, fig. 

 6), postero-lateral margin equally long, the strong lateral spines 

 broken ofi:' at base ; posterior margin slightly obtuse-angled at middle, 

 and furnished at either end with a tooth or spine now broken oflf. 

 Carapace traversed by five strong tuberculate ridges, one median, 

 the others branchial and oblique; median ridge with five strong 

 tubercles, the branchial ridges with three tubercles each ; in addition 

 there are on the anterior half of the carapace about eight ^nailer 

 tubercles on each side; the tubercles are coarsely and densely gran- 

 ulate, the intervening spaces also granulate, the granules spaced and 

 coarser in front and very fine behind. Details of front and orbits 

 lacking. Infero-posterolateral area subtriangular, the surface rising 

 in a point and forming a small tubercle where it meets the posterior 

 of the branchial ridges. Margins finely granulate. 



In its form, strong dorsal ridges, and pair of posterior teeth this 

 species approaches M. hawaiiensis.'^'^ In the fossil the ridges are 



^ Platymera gaudichaudU Milne Edwards, Hist. Nat. Crust., vol. 2, 1837, p. 108. 

 MRathbun, Bull. U. S. Fish Comm. for 1903, part 3, 1906, p. 887, pi. 18, figs. 3 and 4. 



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