A REVIEW OF THE MYSIDACEA 149 



Remarks. — Figure 54 is taken from a specimen from Chesapeake 

 Bay and a comparison with the figures given by Zimmer reveals the 

 closest agreement and leaves no doubt of the identity of the specimens. 

 The species can be distinguished by the combination of characters 

 afforded by the rostral plate, antennal scale, and telson. It is most 

 closely allied to M. pacifica and to Af. elongata. 



METAMYSmOPSIS ELONGATA (Holmes) 



Figure 55 



Mysidopsis elongata Holmes, 1900, p. 226, pi. 4, figs. 77-80. — Tattersall, 1932a, 

 p. 310, figs. 26-38. 



Description. — Body slender ; carapace very slightly produced in front 

 into a short, wide-angled, bluntly pointed rostral plate which does 

 not cover any part of the eyestalks. 



Eyes large, (fig. 55, e) cylindrical; cornea occupying rather less 

 than half of the whole eye. 



Antennular peduncle (fig. 55, /) in the female rather long and 

 slender, first joint longer than the third but shorter than the second 

 and third combined. In the male the antennular peduncle is shorter 

 and stouter than in the female and the setose lobe at the distal end is 

 short and densely fringed with long setae. 



Antennal scale (fig. 55, g) about as long as the antennular peduncle, 

 rather slender and narrow, setose all around, about seven times as 

 long as broad; the distal joint equal to about one-fifth of the whole 

 scale and marked off by a distinct articulation; antennal peduncle 

 (fig. 55, g) shorter than the scale, the terminal joint three-quarters 

 the length of the preceding joint. In the male the antennal scale is 

 somewhat shorter than in the female with the result that the antennal 

 peduncle appears relatively longer, extending beyond the articulation 

 of the distal joint of the scale. 



Labrum forming a rather prominent conical papilla. 



Mandibles (figs. 55, a-b) with a distinct molar process; on the 

 anterior outer angle of the body of the mandible, outside the articu- 

 lation of the palp, is a prominent, sharp, forwardly directed spine. 

 Maxillulae (fig. 55, c) with a very short inner lobe armed with two 

 long setae. Maxillae (fig. 55, d) without exopod and without the 

 setiferous expansion of the lobe from the second joint; palp two- 

 jointed. Maxillipeds (first thoracic limbs) (fig. 55, h) of the true 

 Mysidopsis type, with the second and third joints of the endopod 

 fused. 



Third to the eighth thoracic limbs (fig. 55, j) rather slender, the 

 carpopropodus divided into two by a transverse articulation ; dactylus 

 long and slender, longer than the distal division of the sixth joint. 



