ART. 13. DERMANYSSID MITES OF NORTH AMERICA—-EWING. 11 
The description here given is based on specimens on type slide, 
which were taken from muskrat. Other records are: Many speci- 
mens from muskrat, Florence, Montana, March 27, 1910, Dallas acc. 
2437; one specimen from muskrat, Cambridge, Maryland, March 16, 
1909, by N. Hollister; six specimens from muskrat, Amherst, Massa- 
chusetts, February 16, 1908, by C. W. Hooker. 
TETRAGONYSSUS BERMUDAENSIS (Ewing). 
Female._-Body and appendages uniform light yellowish brown. 
Palpi long. Body sparsely clothed above with moderate setae; 
around the lateral margins is a row of setae which are scarcely as 
long as some of those on the dorsum. Peritreme S-shaped and 
extending to about the middle of second coxae. Sternal plate about 
as broad as long, reaching the third coxae; anterior setae situated on 
anterior margin; middlesetae situated on lateral margins and poste- 
rior setae at the posterolateral corners; all sternal setae very long 
and subequal. Anal plate somewhat triangular in shape; anus 
squarish in front and rounded behind, and situated almost centrally; 
paired setae spinelike and situated near the posterior margin of anus; 
median seta almost enormous and situated at the base of caudal 
area, the latter being crescentic and scobinate. Femur of leg I 
with three dorsal setae, the outer being the longest and the posterior 
the shortest. Length, 0.65 mm.; width, 0.46 mm. 
Male.—Not known. 
Type locality Bermuda. 
Type.—A single female, the only one mounted with dorsal side 
upward on type slide, is here designated as type. 
Description based on individuals on type slide, all of which were 
taken from wood rat, Bermuda, July 9, 1910, by A. O. Gross. 
Genus CERATONYSSUS Ewing. 
CERATONYSSUS CERATOGNATHUS, new species. 
Female.—A medium-sized species. Palpi reaching slightly bey: nd 
first femora; chelicerae with two arms equal and hooked at their 
tips. Dorsal shield divided; posterior shield about as long as ante- 
rior, truncate in front, sides convex, and extending almost to the 
posterior margin of abdomen. Peritreme sinuous, extending to about 
the middle of second coxa. Sternal plate fully twice as broad as 
long; anterior setae situated on the anterior margin; middle setae 
situated just inside of lateral margins and nearer to posterior than 
anterior setae; posterior setae situated on angular corner extensions; 
all sternal setae long and subequal. Anal plate heart-shaped, with 
the anus situated entirely in the anterior half; paired setae situated 
near rim of anus; median seta subequal to paired setae and situated 
