20 TERTIARY COLEOPTERA OF NORTH AMERICA. 



MYAS Dejean. 



Both the species of Myas here described agree closely together and 

 differ from the species now belonging to the United States fauna in the 

 shortness of the antennas, the form of their joints, and the apical elongation 

 of the hind trochanters, but they agree so closely in all other features, 

 including the dilatation of the terminal joint of the labial palpi, and so cer- 

 tainly belong to the Pterostichini by all the available characters, including 

 the three glabrous basal joints of the antennae, the structure of the mentum, 

 the quadrisetose ligula, and the elytra without dorsal puncture, that there 

 can be no doubt they belong either in the nearest neighborhood of Myas 

 or strictly within that genus. 



No other fossil species of the genus are known. It is a small group, 

 with only a single European and two North American species. 



Myas rigefactus sp. nov. 

 PI. I, fig. 4. 



A single specimen shows an inferior surface thi-ough which the striation 

 of the elytra can be seen, and is very perfectly preserved. The short and 

 stout antennse, the enlarged palpi, and the structure of the hind legs appear 

 to agree better with Myas than with any other genus. The general form of 

 the body, with the proportions of head, thorax, and abdomen and the exact 

 shape of the thorax agree perfectly with M. cyanescens Dej. The antennae 

 differ somewhat; they are 11-jointed, about half as long only as the elytra, the 

 first joint a little larger than the others, the terminal oval, the remainder 

 subequal, about half as long again as broad, not very strongly constricted 

 at the base, and squarely truncate apically. Mandibles, labrum, and palpi, 

 as well as the prominence of the prosternum, much as in Myas. Hind 

 coxae attingent at the tip of a broad triangular extension of the abdomen; 

 hind trochanters very large, nearly two-thirds as long as the femora and 

 separated from them by an unusually straight suture, the apex pointed. 

 Faint signs of simple elytral striae seen through the body (not shown in the 

 figure) indicate a close resemblance to M. cyanescens. 



Length of body, 13 mm.; length of elytra, 7.5 mm ; breadth of elytra, 

 5.2 mm.; length of antennae, 3.5 mm. 



Florissant, Colorado; one specimen, No. 9173. 



