A REVIEW OF THE MYSIDACEA 



97 



GASTROSACCUS DISSIMILIS Coifmann 



Figure 29 



? Chlamydopleon aculeatum Obtmann, 1893, p. 25, pi. 2, fig. 1. 

 Gastrosaccus dissimilis Coifmann, 1937, p. 5, fig. 2. 



Occurrence. — Gulf of Mexico, Calcasieu Pass, La., No. 18, W. H. 

 Spaulding collector, November 1906, 1 adult male. 



Distribution. — Off the coast of South America, between Pernambuco 

 and Rio de Janeiro (Coifmann) ; ? mouth of the 

 River Tocantins (Ortmann). The present rec- 

 ord is from the north side of the Gulf of Mexico, 

 off the coast of Louisiana. All these localities 

 suggest that the species is a shallow-water coastal 

 form, probably brackish water in habit. 



Remarks. — This species is very closely related 

 to G. johnsoni but may be distinguished by the 

 presence of a prominent median dorsal spine on 

 the fifth abdominal somite, the longer and more 

 acute rostral plate which extends forward as far 

 as the distal end of the eye, and the somewhat 

 different form of the modified third pleopod of 

 the male. The present specimen agrees closely 

 with the description and figures given by Coif- 

 mann (1937). The third pleopod of the male 

 appears somewhat different from that figured by 

 Coifmann, but this appendage is very difficult 

 to interpret, and, moreover, Coifmann's speci- 

 mens may not have been quite adult. I give here 

 a figure of the third pleopod (fig. 29) in the pres- 

 ent specimen for comparison. For the rest the 

 agreement is so close that I feel justified in iden- 

 tifying it with Coifmann's species. 



In 1893 Ortmann described a mysid under the 

 name Chlamydopleon aculeatum, captured at the 

 mouth of the Tocantins River, on the north coast 

 of South America. The species ought certainly 

 to be referred to the genus Gastrosaccus, but Ort- 

 mann's description is so inadequate that it is 

 impossible to identify the species. I suggest that 

 it is the same as G. dissimilis. There is nothing in Ortmann's descrip- 

 tion and figures against this suggestion except the appearance of the 

 third pleopod of the male in the figure of the whole animal from the 

 lateral view given by Ortmann. The latter gives no detailed separate 

 figure or description of this appendage, and in the figure referred to it 

 appears as an elongate slender appendage which does not suggest the 



Figure 29. — Gastrosaccus 

 dissimilis Coifmann: 

 Third pleopod of male, 

 X 34. 



