288 On Aquatic Carnivorous Coleoptera or Dytiscide. 
Grovur 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, ¢ 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. 
Grour 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. 138 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 may be more or less interrupted transversely so as to leave pale 
fascize, 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. 
