288 On Aquatic Carnivorous Coleoptera or Di/tisciJce. 



Group 1. — Prosternal process short ; male with a coxal file : species found in 

 New World, Nos. 92 to 109. 



A. Species inhabiting the northern half of the New World. Nos. 



92 to 104. 



B. Species inhabiting the southern half of New World. Nos. 105 



to 109, 



N.B. — The coxal file is sometimes very fine and easily overlooked ; 

 in some species it exists in the female as well as in the male, but 

 then it is finer than in the latter sex. Certain species, of which 

 the male is unknown, and at present placed in Group 2, may perhaps 

 have to be transferred to this group. 



Group 2. — Prosternal process short ; no coxal file ; species found in New World. 

 Nos. 110 to 127. 

 N.B. — Of some species included here the male is unknown, and may 

 possibly prove to possess a coxal file, and thus belong to Group 1. 

 L. gentilis is only imperfectly known and as it appears to have a 

 longer prosternal process than the allies, should perhaps be placed 

 in Group 4. 



Group 3. — Prosternal process short, 6 with coxal file ; species inhabiting Old 

 World. No, 128. 



Group 4. — Prosternal process short ; no coxal file : species inhabiting Old World, 

 Nos. 129 to 135, 



Group 5. — Prosternal process with elongate extremity ; no coxal file : species 

 inhabiting the New World, Nos. 136 and 137. 



Group 6. — Prosternal process with elongate extremity; no coxal file; species 

 inhabiting the Old World ; the wing-cases without markings or 

 with markings, but in the latter case the marks are never formed 

 by undulating longitudinal lines. Nos. 13S to 145. 



Group 7. — Prosternal process with elongate extremity ; no coxal file ; species 

 inhabiting the Old World, and with markings on the wing-cases 

 consisting of more or less undulating longitudinal dark lines ; these 

 lines maybe more or less interrupted transversely so as to leave pale 

 fascite, or may extend the whole length ; in certain cases where these 

 dark lines become very thick they are amalgamated or coalesce 

 and then their undulating nature can scarcely be detected. No. 

 155 (Dytiscus variegatus) is the extreme of this case. Nos. 146 

 to 174. 



