2 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 62. 
a?, Chelicerae provided only for piercing, hence without hooks or barbs. 
b'. Chelicerae shearlike in both sexes, never needlelike. 
Subfamily LIPONYSSINAE. 
c!. Body of both sexes entirely covered above by dorsal shield, sternal plate of 
female large and reaching to the third coxae.. Tetragonyssus, new genus. 
c?. Body not entirely covered above by dorsal shield in either sex. 
d', Female with a divided dorsal shield. 
el. Posterior dorsal shield large, covering much of abdomen above; first 
segment of palpus of female with a hornlike process. 
Ceratonyssus, new genus. 
e*. Posterior shield minute; sternal plate with only four setae; first seement 
of palpus of female without any hornlike process. 
Serpenticola, new genus. 
d*. Dorsal shield of female entire. 
e!. Legs stout; tibia I and II less than one and a half times as long as broad; 
femora I and II spined above..........-... Ichoronyssus Kolenati. 
e’, Legs not so stout, especially the first and second pairs, tibiae I more than 
one and a half times as long as broad; femora I and II not spined 
above. 
j'. Body of female with a constriction and incomplete transverse groove 
behind the insertion of the last pair of legs. 
Leiognathus Canestrini. 
f*, Body of female without constriction and incomplete transverse groove. 
Liponyssus Kolenati. 
b?. In the female, chelicerae needlelike; in the male, variously modified but 
always with both arms present........... Subfamily DERMANYSSINAE. 
c!. Dorsal shield of female entire; anus situated in posterior part of anal plate. 
Dermanyssus Dugés. 
c?. Dorsal shield of female divided; anus situated centrally in anal plate. 
Allodermanyssus, new genus. 
One of the new subfamilies here created, the Jxodorhynchinae, is 
established for the new genus /zodorhynchus, which contains a single 
species, also new. This species was taken some years ago in Iowa 
from the eyes of asnake and is quite remarkable. Its general charac- 
ters are almost entirely those of the genus Liponyssus, sensu lato, yet 
the mouth parts are very much like those of some of the generalized 
ticks. The hypostome (fig. 3), while divided, is shaped for piercing 
and is provided with two powerful “holdfast”’ organs in the form 
of recurved hooks. The chelicerae are even more ticklike, being but 
little different from those of some of the true Ixodidae. They are 
short, stout, segmented at the middle, without one chela; and with 
the other, which is movable, provided with three powerful recurved 
hooks. In addition, two small tubercles are present at the base of 
the chela on the chelicera proper. 
Some may doubt the justification of placing this species in the 
Dermanyssidae. ‘True it is that the mouth parts are entirely differ- 
ent from those of the family Dermanyssidae as we have defined the 
family in the past. But if the species is not placed in this group the 
only other alternative is to create for it a new family. This latter 
course hardly appears justified at present in view of the fact that 
