depressed margin before the coxae. With much more justice than to the 

 presternum, Leconte might have referred to the very obvious similarity 

 which exists between Alhyieus and particularly Balbocerus on the one 

 side, and Pico oma on the other, in the large size, great convexity, 

 smoothness, and brightness of the eyes, though this is as little decisive, 

 systematically, as the similarity mentioned by Leconte between the two 

 genera in the form of the anterior tibia and middle tarsi, for this can be 

 equalled in a still more striking manner in another group of the Lamel- 

 licorn s (Melt lonlhidce ) . 



Under no circumstances can these analogies, so far as they really 

 exist, weigh against the fundamental differences, which two of the most 

 important structures— the antennae and mouth parts — show at a glance 

 to exist between the Geoirypini and Phocoma, and with perfect right did 

 Leconte insist that on these characters it was impossible to unite Pleo- 

 coma with that Coprophagus group. The antennae have nothing in 

 common except the number of joints, eleven. With all the variations in 

 form of club offered by the Geotrypid genera, it is yet constantly three- 

 jointed, and always sharply limited from the funicle or stem, while in 

 Pleocoma it varies from four to seven joints in the species and runs grad- 

 ually into the funicle or stem — a peculiarity which, omitting the Lucanini 

 and Passalini, is found only in the Melolonihida; among the Scarabaids. 

 In like way the mouth parts are diametrically opposed in structure: in 

 the Geoirypini a large, transverse, horizontal labrum, broad, free, prom- 

 inent mandibles, well developed, in comparison with the palpi large 

 maxilla;, the inner lobe appearing furcate owing to a deep incision, and 

 finally a large, also transversely developed mentum (compare Klug, Ueber 

 die Gattungen Athyreus und Balboceras, Taf. II, Fig. I bis IVa, b) ; in 

 Pleocoma on the contrary a very small, rather long, deflexed labrum, en- 

 tirely rudimentary, concealed mandibles, small maxillae, reaching scarcely 

 to the end of the first palpal joint, the inner not split, and a very small, 

 i >bl< >ng mentum. 



When therefore the genus Pleocoma neither in the position of the stig- 

 mata, nor in any other important structural character agrees with the 

 /<////. but is to he ranged with the Scarabaeidae pleurosticti ; the 

 next question would be, whether it is, in this group, entitled to take- 

 rank as a distinct tribe (Pleocomini). This question also is to be 

 answered by a decided negative, because those very characters used by 

 Leconte to separate the genus from the Geoirypini are identical with cha- 

 racteristic peculiarities of some of the Melolonthidce. By the structure of 

 die antennae alone Pleocoma is at once excluded from every other group 

 of pleurosticti Lamellicornes (DynasHni, Melitophila and Rutelint) because 

 in all those the club is distinctly three- join ted, and sharply defined against 



