584 PROCEEDINGS OF THE NATIONAL MUSEUM vol. in 



Description.— Agreeing with the generic description except for the 

 following modifications: 



Head: Juga dorsally without fine carina marginally, margin thick- 

 ened, usually calloused, sometimes with a submarginal line; in all 

 species (except Joratus and megalocephalus) with one submarginal 

 setigerous puncture; labial length variable from between middle of 

 mesosternum to sternite IV. 



Mesopleuron: Evaporatorium extensive, extending along posterior 

 margin of segment into posterolateral angle; posterior margin with 

 crenulations finer and closer set than in subgenus Pseudopangaeus 

 (fig. 106). 



Legs: Posterior tibia of both sexes simple; femora not tuberculate 

 ventrally. 



Type of genus. — Aethus americanus St^l (1860, p. 12), here desig- 

 nated. 



Distribution.- — Specimens at hand indicate the range of this sub- 

 genus as extending from Mexico south through Central America into 

 northern Brazil and eastward into the West Indies, with a single 

 specimen labeled from Florida. 



Discussion. — The form of the jugal margin seen in the members 

 of this subgenus appears to be almost unique within the American 

 forms of the subfamily Cydninae appearuig only in certain Melanae- 

 thus. In most species the juga have a fine but distinct dorsal carina 

 at the very margin of the head. In the subgenus Ecarinoceps, how- 

 ever, such a carina is either lacldng or distinctly submarginal and 

 incomplete when the head is viewed at right angles to its dorsal 

 surface. This feature is easily interpreted in all included species. 



Key to species of subgenus Dallasiellus (Ecarinoceps) 



1. Mesopleural evaporatorium reaching to lateral margin of segment .... 2 

 Mesopleural evaporatorium approaching but not attaining lateral margin of 



segment (fig. 105) 6 



2. Labium very long, reaching to sternite IV; anterior convexity of propleuron 



with numerous, close-set, moderate punctures. 



longirostris, new species (p. 591) 



Labium shorter, not surpassing middle coxae; anterior convexity of propleuron 



most impunctate 3 



3. Costa with one setigerous puncture 4 



Costa with two setigerous punctures 5 



4. Head across eyes more than half pronotal width, anterior outline broadly 



rounded or semicircular (fig. 62) . . megalocephalus, new species (p. 592) 

 Head across eyes less than half pronotal width. . laevis, new species (p. 589) 



5. Bucculae higher than labial II, terminated abruptly posteriorly (as in fig. 23) ; 



size larger, length of body, 8.2-8.8 reflexus, new species (p. 594) 



Bucculae lower than labial II, evanescent posteriorly; smaller, length of body, 

 6.0-6.7 ' scitus (Walker) (p. 587) 



