20 Memoirs on the Coleoptera 



Tribe Optatini. 



This tribe is moderate in regard to numbers but rather diversified 

 in appearance, recalling the Centrinini very strongly in general 

 habitus of the body, and to some extent in the form of the mandibles, 

 but distinguishable by a number of features, no one of which is 

 however constant. The two most important characters are the 

 contiguous anterior coxae and absence of male prosternal spines in 

 the Optatini, but there are several genera, and especially Eury- 

 pages, where the coxae become rather conspicuously separated and 

 there are many Centrinides having no vestige of prosternal spines 

 in the male. There is, however, an almost undefinable difference 

 of facies, depending upon sculpture or peculiarities of the vestiture, 

 which, though no more constant that the others, form some of the 

 elements that in combination will generally indicate the correct 

 assignment of any particular genus. The species are much larger 

 than in the Cyrionichini — included with the "Optatides" by Mr. 

 Champion — in fact including the largest known in the Barinae. 

 There is, besides this, scarcely a vestige of similarity in habitus 

 between the two tribes, although in both of them the femora are 

 spiculate beneath throughout and the pygidium completely con- 

 cealed as in Centrinini. 



The mandibles are not strongly decussate, with rounded outline 

 when closed as they are in Cyrionichini, but are straight within, and 

 as a rule — excepted however in Costovia and Pseudoptatus, where the 

 mandibles in each case are peculiar — form an angulation when 

 closed, somewhat as in many of the Centrinini. The inner edge 

 may however be strongly dentate, as in Syprestia and Optatus, the 

 tooth becoming long and slender in Pseudoptatus, where the man- 

 dibles when closed present a broadly rounded outline, or, with the 

 edge but slightly irregular, as in Lydamis; in parvula, in fact, the 

 edges are virtually even and form an almost perfect straight line 

 of contact when closed. In Costovia the mandibles are acuminate 

 at tip and dentate within and have assumed a more vertical plane 

 of action, somewhat as in Balaninus, which might have been 

 predicated by the similarly extremely slender cylindrical beak, but 

 the general aspect of this .genus and the absolutely contiguous 

 anterior coxae, with the strongly ascending mes-epimera of the 

 Barinae, show that it must be placed nevertheless in the Optatini; 

 all of which goes to indicate that in some parts of the Barid series 

 the form of the mandibles does not have the systematic value that 

 it has elsewhere. In other words, as in so many parts of the 

 Coleoptera, groups can be formulated more naturally on generalities 

 than on special structures. 



The genera included in the material at hand are the following: 



