CYDNIDAE OF THE WESTERN HEMISPHERE — FROESCHNER 573 



secondarily on other features possessed by groups of species, gives a 

 truer picture of relationships than any other system offered. This 

 arrangement has the additional merit of keeping to a minimum the 

 number of monobasic genera in this morphologically homogeneous 

 family. 



All American species of Dallasiellus differ from the type species of 

 Geocnethus Horv^th (0. obesus Horvdth) in that the metapleural 

 evaporatorium is complete, while in Geocnethus obesus it has an ante- 

 rior, submarginal, polished band (suggestive of Rhytidoporus) extend- 

 ing laterally from the tip of a fold just anterior to the apex of the 

 osteolar peritreme. All Western Hemisphere species that have been 

 described in Geocnethus fit readily into Dallasiellus as here defined. 



Dallasiellus contains three major groups of species that grade into 

 each other by transitional combinations of structural details, thus 

 preventing the establishment of full genera. To point out this group- 

 ing, the author has felt obligated to divide the genus into three sub- 

 genera which may be separated by the following key: 



Key to the subgenera of Dallasiellus ^ 



1. With the combination of very coarse, widely separated crenulations sub- 



laterally on posterior margin of mesopleuron, and a transverse, submarginal, 

 polished band interrupting mesopleural evaporatorium posteriorly (fig. 106) 

 (male hind tibia with strong, subbasal angulation on posteroventral margin 



as in fig. 148) Pseudopangaeus, new subgenus (p. 573) 



Without the combination of coarse crenulations and posterior interruption 

 mentioned above, usually with neither (male hind tibia never with subbasal 

 ventral angulation) 2 



2. Margin of jugum with fine, marginal carina dorsally from eye to apex. 



Dallasiellus Berg (p. 595) 

 Margin of jugum thick, calloused, ecarinate or with partial carina (not reach- 

 ing eyes) located submarginally . . . Ecarinoceps, new subgenus (p. 583) 



Dallasiellus (Pseudopangaeus), new subgenus 



Diagnosis. — The members of this subgenus differs from all other 

 species in Dallasiellus by the combination of strong crenulations and 

 evaporatorial interruption mentioned in the key and illustrated by 

 figure 106. The males can be more readily separated by the presence 

 of a strong angulation ventrally on the posterior tibia (fig. 148). 



» The Cyd7ius insularis which Westwood (1837, p. 19) described from "Insula Sti. Vinccntii" apparently 

 also belongs to this genus. Dr. Graham's notes on the type in the collection at Oxford University show it 

 to lack a terminal modification of the peritreme and to have an incomplete row of setigerous punctures on 

 the submargin of the jugum. These features coupled with the small size will permit no other assignment. 

 Bat as yet, not enough information is at hand to place it exactly. It most probably belongs in either the 

 subgenus Ecarinoceps or the subgenus Dallasiellus. If the former, it will run to couplet 5 in the key to 

 species but will differ from both forms found there in possessing a partial row of setigerous pimctures on the 

 submargin of the Jugum. If it belongs to Dallasiellus it will probably run to lugubris in couplet 14 of the key 

 to species. 



