36 BULLETIN 138^ UNITED STATES NATIONAL MUSEUM 



(pi. 9, hg. 0). Surface lobulate, as follows: One hepatic lobule, 

 obliquely transversely oval; one epibranchial, parallel to the hepatic 

 but wider, and having partly attached to its inner end at right 

 angles a small mesobranchial lobule which occupies the inner angle 

 of the branchial region; the metabranchial region is almost covered 

 by a large lobule. The protogastric lobes each have two linear 

 parallel tubercles, the inner pair longer than the outer and near the 

 inner edge of the subregion, the outer pair rising in the middle to 

 a subacute tubercle ; narrow part of mesogastric region constricted, 

 end acuminate, terminating in a broad frontal furrow; metagastric 

 lobes each crossed by an oblique line of about seven coarse granules. 

 The cardiac region bears three acute tubercles forming an equi- 

 lateral triangle, the posterior tubercle median. The regions and 

 most of the lobules are separated by deep, broad furrows and are 

 covered with fine depressed granules. The three antero-lateral teeth 

 are set off by a furrow; the first or orbital tooth points forward, 

 the second is shorter and points obliquely forward and outward; 

 while the third, at the lateral angle, is directed outward and upward. 

 Outside the epibranchial lobe there is a small low lobule just above 

 the postero-lateral margin beyond which it does not project. Front 

 well advanced beyond orbit, subtruncate, medially furrowed ; the 

 orbital margin slopes gradually backvrard to 'the outer tooth, except 

 for a shallow prominence near its middle; eyestalk stout (3993). 

 Posterior margin concave between attachments of legs of last pair. 



The smallest specimen (5682) is less than 5 mm. long; the lobules 

 are arranged as in the holotype, the front is advanced and sub- 

 truncate, details of lateral teeth are obscured. 



The largest specimen — that figured by Weaver — shows the entire 

 outline of the orbit with its strong, outer, conical tooth, also the 

 lateral teeth and areolations of the carapace (pi. 9, fig. 5). 



Medsurements. — Length of carapace of holotype in median line, 

 front probably incomplete, 14 mm.; greatest width of same, at last 

 pair of lateral teeth, 20 mm.; width across front and orbits 17 nmi. 

 Width of carapace of specimen from Loc. 1817, 23.2 mm. ; of carapace 

 TMiT,28.2mm. 



Occuni'ence. — California ; Eocene series : 



Salt Creek, 314 miles north-northeast of Joaquin Eocks, Fresno 

 County; south part of northwest quarter, section 15, township 18 

 south, range 14 east; Eocene series; 1909; one carapace, holotype; 

 Cat. No. 353351, U.S.N.M. 



Salt Creek, 81^4 miles northwest of Oil City, Fresno County; cara- 

 pace of very small specimen ; Cat, No. 353352, U.S.N.M. 



Southeast quarter of northwest quarter of section 15, on branch 

 of Salt Creek, township 18 south, range 14 east, Mount Diablo base 

 line and meridian, Coalinga Quadrangle, Fresno County; near base 



