176 BULLETIN" 103, UNITED STATES NATIONAL MUSEUM. 



THAUMASTOPLAX PRIMA, new species. 



Plate 66, figs. 15-18. 



Type-locality. — Panama Canal Zone. Las Cascadas section, Gail- 

 lard Cut. From lowest i'ossiliferous bed; third bed below lowest 

 limestone beds separated by rows of nodules. Lower part of upper 

 half of Culebra formation. Oligocene series. D. F. MacDonald 

 and T. W. Vaughan, collectors. 1911. Station 6020a. 



Measurements. — Length of carapace, paratype, 12.2 mm. (ap- 

 prox.) ; width, 18 mm. (approx.) The holotype is a little wider, 

 about 19.6 mm., but the length can not be measured as the front part 

 of the carapace is not visible. 



Holotype and paratype. — Carapace about \\ times as broad as long, 

 longitudinally very convex, from side to side nearly horizontal. Up- 

 per surface not bordered by a definite line; H-shaped depression in 

 the center of the carapace deep; surface deeply punctate, punctae 

 crowded near the margins, sparse near the middle. Fronto-orbital 

 distance about two-fifths as great as the extreme width of the cara- 

 pace. Antero-lateral margins long, arcuate ; postero-lateral margins 

 subparallel; posterior margin slightly convex. Front deflexed and 

 widening a little from the base of the eyestalks downward. The 

 orbit is about as wide as the narrowest part of the front and is filled 

 by the eyestalk ; its upper margin is transverse. 



Chelipeds short, when flexed scarcely reaching beyond the outer 

 end of the orbit; carpus very large, convex, smooth, and punctate; 

 chela small, not much longer than carpus and considerably nar- 

 rower; finger shorter than palm; the end of the finger is, however, 

 not visible. The merus of the first leg reaches quite to the end of 

 the carpus of the cheliped, its upper margin has a row of small 

 conical tubercles or granules, and there is a cluster of granules near 

 the articulation with the carpus. The merus of the second leg 

 reaches a little beyond that of the first, and is very much stronger; 

 it also has a superior row of granules and a few granules on the 

 outer surface; carpus elongate, about half as long as merus; pro- 

 podus as wide as the greatest width of the carpus; only a portion 

 of it is visible. Third leg very much shorter and slenderer, its 

 carpus reaching little beyond the merus of the second pair ; its merus, 

 as well as that of the second pair, is longitudinally grooved. 



The above description is made from two specimens from the same 

 place. Each specimen was enclosed in a nodule which is broken in 

 two. The holotype shows the upper surface of the carapace (ex- 

 cept the front part) , portions of the left cheliped, and of the 3 legs 

 of both sides. The nodule is not large enough to have included the 

 whole of the legs in their extended position. Cat. No. 324227, 

 U.S.N.M. The paratype shows the carapace only; there is no trace 



