42 



riiOCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVIII. 



Mo.st of the .species come from the French coasts or the Atlantic 

 Ocean: one. was described from fresh water. A few are from other 

 reg^ions, and doubtless, as the}' are^more collected, the family will be 

 of considerable size. ILiJucorm^ the largest genus, contains about 

 fifty species, several of which bear some resen:blance to Sc^ttoverte.i- in 

 the Oribatid^e. Most of them are marked with lirown, reddish, or 

 black. Dr. E. Trouessart, of Paris, has pul>lished very largely upon 

 them. l*ackard d(>.scribed, under the name of TliaJassantchna rerrilVK 

 a species of IlaJacanis from the coast of Maine; it was found on algie. 



Superfamily IXODOIDEA. 



The members of this group, commoidy known as ticks, are of all 

 Acarians the most familiar to ordinary people. Their body is covered 

 l)y a tough, leathery skin, which in the female is capable of great 

 extension. The ticks (before distention) are of a somewhat triangular 





Fig. 71. — Argas mimatus, from 



BELOW. 



Fig. 



-Ornithodoros megnixi: nymphal form, and 

 DETAILS (Marx I. 



outline, moderately flat, with prominent, slender legs and a beak-like 

 rostrum in front. On the anterior part of the dorsum there is a cor- 

 neous piece or shield that may represent the cephalothorax. This is 

 known as the scutum, and is absent in the family Argasidte. With 

 the male this scutum covers the greater part of the dorsum. Articu- 

 lated to the anterior margin of the scutum, usually within an emargi- 

 nation, is a small, transverse piece, the capitulum or head. The 

 posterior corners of the capitulum project backward in spines. In the 

 female ticks there are on the dorsum of the capitulum two pitted areas, 

 known as the porose areas. The capitulum bears the palpi on each 

 -side and the mandibular sheaths. The latter include the mandibles 



