ISO Dr. E. L. Trouessart — Synoptical Revision 



GROUP A a. — Rostrum small, triangular, conical, with rather 

 short palpi, the last joint conical at its point only, and 

 very little longer than the penultimate. A single exotic 

 species, which, by the shortness of its palpi, approaches 

 the genus Coloboceras. 



1. Halacarus parvirostris, sp. n. 



Char. Rostrum presenting the characters of the group ; 

 palpi with the last joint cylindrical for four fifths of its length, 

 and terminating suddenly in a very small point. Hypostome 

 groove-like, constricted in front, truncated at the level of the 

 base of the last joint of the palpi. Epistome presenting an 

 obtuse, rounded projection at the level of the base of the 

 rostrum. Anterior legs shorter and more robust than the 

 posterior, with the second joint inflated, and the fourth nearly 

 triangular, furnished with a spine beneath ; claws with no 

 ciliated comb ; no ungueal groove on the tarsus. Dermal 

 plates finely punctured in indistinct rosettes. Total length 

 0-40 millim. 



Hob. On seaweeds from New Zealand sent to the Museum 

 at Paris (M. Harioi). This species is, in all respects, very 

 distinct from the two species described by Chilton, which will 

 be mentioned further on. 



GEOUr A. — Rostrum narrow, with the lateral margins parallel 

 as far as the basal region ; hypostome compressed, longer 

 than the basal part of the rostrum ; third joint of the palpi 

 bearing at its antero-internal angle a very fine spine 

 directed obliquely forward ; fourth joint sabre-shaped. 

 Sexual aperture projecting in the form of a bivalved bulb. 

 Two species. 



2. Halacarus Murrayi. 

 Lolimann (8), p. 70, figs. 83, 80. 



Char. Those of the group ; anus terminal. Legs slender, 

 the posterior very long ; claws much elongated, pectinate ; no 

 ungueal groove on the tarsi. Dermal plates feebly developed. 

 Ocular plates with a single cornea, and in the inner angle a 

 large pore* with a small chitinous plate behind it. All the 

 hairs of the legs very long and very slender, not spinous. Total 

 length' 0-52-0-57 millim. 



Hob. Baltic, Kiel (Lohmann) , in the region of Red Sea- 



* To see these details of the chitinous cuirass of the Halacaridaa it is 

 indispensable to treat them with a more or less concentrated solution of 

 potash, which renders them colourless and transparent. 



