168 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



GATUNIIDAE, new family. 

 Characters of the type genus, Gatunia. 



GATUNIA, new genus. 



Carapace of the customary Cancrid outline, that is, transversely 

 oval, with a narrow, dentate front (between the orbits) ; orbits nar- 

 row, with a forward inclination; antero-lateral margins arcuate r 

 longer than the postero-lateral, and armed with 8 teeth, including 

 the orbital ' tooth ; postero-lateral margins strongly convergent. 

 Genital region very narrow. Carapace without transverse ridges. 



Outer maxilliped with the ischium greatly elongate, and longi- 

 tudinally grooved. 



Chelipeds massive; palms thick, not flattened on the inner side, 

 devoid of ridges on the outer side. 



Last pair of feet with the propodus and dactylus flattened and 

 broadened to form a swimming organ as in the Portunids. 



Abdomen of the male with the third, fourth, and fifth segments 

 fused. 



This genus resembles the family Cancridae in the form of the- 

 carapace, front and orbits ; while the swimming paddles and the ab- 

 domen are like those of the Portunidae. The chelipeds approach 

 those of the genus Scylla in their massiveness, long fingers and lack 

 of costae, but the absence of spines gives them the appearance of 

 many of the Xanthidae. 



Type of the genus. Gatunia proavita Rathbun. 



GATUNIA PROAVITA, new species. 

 Plates 54-56 ; plate 58, figs. 16 and 17. 



Type-locality. Gatun formation, near Gatun Dam, Panama Canal 

 Zone. Miocene series. Collected by one of the workmen and 

 shipped by D. F. Macdonald. Station 5659. One specimen (holo- 

 type), nearly complete. Cat. No. 324289, TJ.S.KM. 



Measurements. Length of carapace, from tip of submedian teeth., 

 133.2 mm.; from median- sinus, 128.3 mm.; width, between tips of 

 teeth of posterior pair, 182.5 mm. ; width between teeth of penulti- 

 mate pair, the same. 



Holotype. Carapace about 1 times as wide as long; antero-lateral 

 margin strongly arched, cut into 7 strong teeth, besides the tooth; 

 at the outer angle of the orbit ; teeth similar in shape, having a convex 

 posterior and a concave anterior margin, tip acute; the 7 teeth in- 

 crease in size from the first to the fifth and then diminish to the 



