A REVIEW OF THE MYSIDACEA 



209 



Distribution. — Known only from the coast of California. 

 Remarks. — This species is closely related to A. sculpta and it will 

 suffice if the main differences are enumerated, as follows: 



(1) The form of the body is more compact and robust. 



(2) The somites of the pleon are furnished with folds and ridges, 

 three on the first somite and two on the succeeding somites. There 

 are, however, no spines on the fourth and fifth somites, and the sixth 

 somite has an anterior median triangular plate and a posterior sculp- 

 tured region but no pair of median blunt spines. 



(3) The antennal scale (fig. 86, d) is five times as long as broad. 



Figure 85. — Acanthomysis sculpta (Tattersall) : a, Distal joints of endopod of one of pos- 

 terior thoracic limbs, X 40; b, uropods, X 40. 



(4) The endopods of the third to the eighth thoracic limbs (fig. 

 87, a) have the sixth joint divided into four or five subjoints. 



(5) The telson (fig. 87, c) is narrowly triangular in shape, two and 

 a half times as long as broad at the base. The apex is narrowly trun- 

 cate and armed with two pairs of spines, the inner pair of which is 

 less than half as long as the outer. The lateral are armed throughout 

 their whole length with numerous large spines which increase consid- 

 erably in length toward the apex. On the distal two-thirds of the 

 margins the spaces between the large spines are occupied by two, three, 

 or four smaller spines. 



(6) The inner uropod (fig. 87, b) has four or five strong spines on its 

 lower margin near the statocyst. 



