DR. F. LEUTHNEE ON THE ODONTOLABINI. 433 



The head has no occipital crest, as in Lucanus, and no cephalic prominences, as 

 in Hexarthrius ; but the frontal ridge is strongly developed in large specimens ; in 

 small ones the head is flattened. The eyes are large, and separated by a canthus of 

 variable width, but narrowest in large specimens. The spine behind the eye is very 

 characteristic, but is scarcely developed in 0. carinatus and 0. ceratus. The clypeus is 

 deeply emarginate, and distinctly separated from the front. The labrum projects 

 between the mandibles, as far as their shape will allow, and it is frequently contracted 

 into a true epistoma. The mandibles are large, and differently developed, varying 

 both in shape and size. Sometimes there is an unbroken series of forms of mandibles, 

 from the smallest, which resemble the female, to the largest and most highly developed ; 

 but in other cases they exhibit several forms which cannot be connected by inter- 

 mediate links. 



In order to facilitate comparison 1 have distinguished the four forms of mandibles 

 which are most frequently differentiated as follows: — 



(1) Forma telodonta (tIXoc, end ; oSouc, tooth). The most highly developed form ; 



the terminal form i. (PI. LXXXIX. fig. 1.) 



(2) Forma mesodonta {fieaoc, middle). In this form a strongly developed tooth 



projects inwards from the middle of the mandibles. (PI. LXXXIX. fig. 3.) 



(3) Forma amphiodonta {afKplc, on both sides). Mandibles with teeth at the tip 



and at the base only. (PL LXXXIX. fig. 5.) 



(4) Forma priodonta (irgihtv, saw). Inner side of the mandibles toothed. (PL 



LXXXIX. figs. 6, 7.) 



The second and third forms may occur conjointly {amphio-mesodonta), and the fourth 

 form may be either regularly (isodont) or irregularly (anisodont) toothed. (PL XCII. 

 fig. 8.) 



The prothorax is generally broad, and is often provided with two or three lateral 

 spines (as in 0. alces and others). It frequently happens that the middle spine only is 

 developed, the sides being rounded off in many species. 



The prosternal process is generally well developed, as in 0. alces and 0. dalmani, 

 and projects distinctly downwards and backwards. The elytra are broad, with the sides 

 margined, and are generally smooth and shining, and are most frequently black, althougli 

 sometimes bicolorous or tricolorous. The elytra are hairy in 0. dalmani, and sometimes 

 in 0. carinatus ; in 0. striatus the lines on the elytra are alternately smooth and hairy. 

 0. ceratus exhibits a metallic lustre. The tibise of the long front legs are long and 

 straight or slightly curved inwards. 



The small males with priodont mandibles are often so similar to the females that 

 they have been frequently described as such by various authors ; but they may always 



' Comp. p. 397 (anteu). 



VOL. XI. — PART XI. No. 7. — Xovember, 1885. 3 s 



