194 Mr. T. Vernon WoUaston on the 



apical one usually acuminated). The exact form and length of 

 the sterna, the relative distance of the hinder coxse from each 

 other, the proportions of the abdominal segments and tarsal joints, 

 the development of the eyes, wings and scutellum, the gibbosities 

 of the pronotum, and the occasional peculiarities of the sexes, are 

 all points (and very significant ones) from which the diagnoses of 

 the several genera have principally to be compiled. 



The Plinidce constitute a most important group in the Canary 

 Islands, — as indeed may be gathered from the fact, that, out of 

 the fourteen members hitherto detected there are indications of no 

 less than four genera which have not, up to the present time, been 

 enunciated ; three of which, moreover, contain features of a most 

 anomalous kind, and hitherto quite unprecedented in this small 

 family. In attempting to collocate them, however, inter se, they 

 would appear to arrange themselves in a circle, — the most ab- 

 normal characters fading-off in two opposite directions, amongst 

 forms which gradually coalesce. Thus, commencing, for instance, 

 with the extraordinary genus Casapus, distinguished {inter alia) by 

 its apically-excavated labial-palpi, its obtuse mandibles, and the 

 swollen basal-joint of its two hinder male-feet, we are led on, by 

 Dignomus (which combines this scooped-out apex of the labial- 

 palpi with the outward configuration, and general details of 

 Ftinus), into Ptinus proper. From Ptinus the passage is simple 

 enough to Mezium ; and from thence into Nitpus and Sphcericus 

 (which are almost identical, except that the former has a dimi- 

 nished number of joints both for its antennae and posterior male- 

 feet). From Sphcericus we glide very naturally into Piarus, — 

 which possesses most of the peculiarities of the former, together 

 with some of the distinguishing features of the next genus, Piotes ; 

 which last, in the immensely expanded first-joint of its hinder 

 male-tarsi, no less than its nodose-costate prothorax, the obsolete 

 subsetulose ridges at the base of its elytra, and its undistinguish- 

 able scutellum [ — though not, however, in the construction of its 

 mandibles and labial-palpi], brings us back again to Casapus. 



Genus Casapus, nov. gen. (PI. VIII. fig. 1, 2, 3.) 



Corpus (inter Piinidas) magnuvu, vel ellipticum vel elongato- 

 ovatum, politum, plus minus parce squamosum et pilosum 

 necnon ad humeros setosum, apterum : capite deflexo ; oculis 

 subrotundatis, vix prominulis : prat hor ace post'ice plus minus 

 gradatim angustiore, basin versus plus minus 4-nodoso-cos- 

 tato : scutello baud observando : elytris subconnatis, ad basin 

 plus minus longitudinaliter costatis : metasterno brevi, postice 



4. 



