CUMACEA FROM THE COPEXUAGEN" MUSEUM. 361 



Type-species S. depressum, sp. n. 



This genus bears the same relation to Nannastacus that Zf/f/osiphonhears to Cyclaspis. 

 IVo males have yet been identified, but the analogy of Zipjosiphon makes it probable 

 that the division of the respiratory openings will be found in that sex also. In the 

 type-species the second maxilliped has a distinct ischium, but for reasons already 

 mentioned (p. 351j I prefer not to regard this character as of generic value. 



Key to the Species o/*Schizotrema. 



A. Carapace very broad and depressed ; a couspicuous lateral series of spines 



on carapace, posterior thoracic somites, and abdomen ; peduncle of 



uropod longer than last somite S. depressiim, sp. n. 



B. Carapace less depressed ; no conspicuous lateral spines on carapace or 



abdomen ; peduncle of uropod not more than half as long as last somite. 



a. Surface of body with numerous small spines and tubercles; antero- 



lateral angle of carapace produced as a stout cylindrical process . . S. bifrons, sp. n. 



b. Surface of body for the most part smooth ; antero-lateral angle 



produced as a slender tooth S. sordidum, sp. u. 



ScuizoTKEMA DEPRESSUM, sp. n. (Plate XXXIV. figs. 14-17.) 



Description of adult Female. — Total length 1-5 mm. 



Carapace a little less than one-third of total length, very broad and depressed. 

 The pseudorostrum, seen from the side, is very short and truncate, directed obliquely 

 upwards. Seen from above, the two parts of the pseudorostrum are widely separated, 

 each completely surrounding the respiratory orifice, from which a long branchial siphon 

 is protruded. The antennal notch is obsolete, the antero-lateral margin descending 

 nearly vertically to the rounded antero-lateral corner, which carries a stout curved 

 spine. A series of spines runs backwards from this along the lateral edge of the 

 carapace, diminishing in size until the last two or three, which are again larijer. The 

 darkly-pigmented eyes lie just behind the branchial openings; the number of corneal 

 facets could not be determined. The surface of the carapace is everywhere minutely 

 granular, and, in some specimens, there is found on each of the branchial regions and 

 on an elevation of the dorso-lateral surface on each side behind the eve a lar^e 

 granule or vesicular outgrowth, which apparently is very easily detached. 



The free thoracic somites are very broad and depressed, their pleural plates armed 

 with large spines. 



The abdomen is shorter than the cephalothoracic region. The somites, with 

 exception of the first, have a series of stout spines on each side ; the last somite is 

 shorter than the penultimate and is rounded posteriorly. 



Long setic are set here and there over the surface of the body, and a very conspicuous 

 row of them fringes the lateral margins of carapace, free thoracic somites, and abdomen. 



