of the Family Halacaridse. 1 75 



the genital organ (H. Lohmann). The legs are generally 

 shorter in the nymphs, which have in each limb one joint 

 less * than the adults. Otherwise the construction of the 

 rostrum, tarsi, and dermal plates is very nearly the same as in 

 the adult. 



Many individuals at the moment of their capture have the 

 body and limbs incrusted with a sort of mud, in the midst of 

 which Acinetse are sometimes fixed in considerable numbers. 



Synopsis of the Genera aud Species of the 

 Family Halacaridse. 



Genus Rhombognathus, Trt. 1888. 



Trouessart (7), November 1888, p. 754. 

 Aletes, Lohmann (8), December 1888, p. 51. 

 Pachygnathus, pt., Gosse (1), 1855. 



Char. Rostrum short, conical, with the maxillary palpi 

 lateral, applied closely along the mandibles, which are termi- 

 nated by a hooked claw. Tarsus separated from the double 

 terminal claw by an additional cylindrical, slender, and more 

 or less elongated joint. 



Seven species, of which four occur on the French coasts. 

 Most of them are of a greenish-black colour, of small size, 

 and of a short, thickset form. 



1. Rhombognathus pascens. 

 Ateles pascens, Lohm. (8), p. 64, figs. 64, 70. 



Char. Claws angularly recurved ; additional piece of the 

 tarsus produced in the form of a hook only in the anterior 

 feet. Coxa3 of the first pair of legs united into a single 

 ventral plate. Ocular plates with only a single cornea. 

 Total length 0*35 millim. 



Hab. Atlantic coasts, France : Baie de Port-lin, near Le 

 Croisic, upon stranded red Alga? (E. Chevreux), rather rare. 

 Shore of the Channel, Etretat (Mile. C. Trouessart). Baltic, 

 Kiel (Lohmann), upon sandy shores, living and stranded red 

 Algas. 



2. Rhombognathus Seahami. 



Pachygnathus Seahami, Hodge (2), 1860. 

 Aletes Seahami, Lohm. (8) p. 57, figs. 88, 94. 



Char. Claws angularly recurved ; additional piece of the 



* Four, instead oijive as in the adult. 



13* 



