2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 78 



LOBONOTUS MEXICANUS, new species 



Plate 1 



Description of holotype. — The length of the carapace equals the 

 width at the tip of the third or hepatic tooth. The surface is divided 

 into a certain number of elevations all of which, as well as the mar- 

 ginal teeth, are surmounted by coarse granules. A median furrow 

 runs from the mesogastric region to the frontal emargination. An 

 oblique ridge occupies the hepatic region, and a larger one parallel 

 to it fills the epibranchial region ; a small crescentic furrow defines 

 the inner branchial lobe, and a larger swelling occupies the remainder 

 of the branchial region; a long narrow lobule is above and parallel 

 to the margin of the intestinal region. Antero-lateral margin thick, 

 fourth tooth much the largest, second tooth below the level of first 

 and third. Front deflexed at the middle, outer corner turned down 

 and separated by a groove from the obtuse inner angle of the orbit; 

 two superior orbital furrows and one inferior and lateral. 



Outer margin of ischium-merus of the endognath of the external 

 maxilliped concave, ischial furrow deep and wide. Merus of cheliped 

 with a large spine (broken off) on the upper margin distant from 

 the extremity; upper-outer surface of carpus large, longer than 

 wide, surface rough with tubercles or broken-off spines, a groove 

 parallel to distal margin. Palm with straight lower margin, outer 

 surface very convex from top to bottom and with longitudinal rows 

 of spines or tubercles; fixed finger elongate (broken), inclined a 

 little downward toward the tip. Outer ends of first segment of male 

 abdomen oblique, of second segment slightly convex, of third segment 

 angled ; sides concave from third to seventh segment, the latter sub- 

 triangular, broader than long and broadest beyond the articulation. 



Measwevients. — Total length of carapace 33.8, width of same 39.7, 

 fronto-orbital width 22.2, width of front 11.2 mm. 



Occurrence. — Lower California : Ranchito on south side of Arroyo 

 Colorado between ranches Matanzo and Colorado; upper Eocene; 

 November 11, 1920 ; Coll. No. 9692. The holotype shows upper and 

 lower surfaces of the body, a portion of the left cheliped and frag- 

 ments of the legs. Cat. No. 371096, U. S. N. M. 



Relation. — Carapace narrower than in L. sculptus A. Milne 

 Edwards,^ from the upper Oligocene - of Haiti, antero-lateral teeth 

 shallow, thick and blunt, instead of spiniform, the epigastric lobes 

 narrow instead of wide, the immovable finger only slightly deflexed. 



lAnn. Sci. Nat., Zool., ser. 4, vol. 20, 1863, pi. 10, figs. 1-16; ser. 5, vol. 1, 1864, p. 40. 



2 According to Glaessner in Pompeckj's Fossiliuxa Catalogus, 1, Animalia, part 41, 1929, 

 p. 451. A. Milne Edwards gives middle Tertiary, while the specimens in the Museum of 

 the Philadelphia Academy of Natural Science were labeled " probably lower Miocene " by 

 their collector. 



