MYSIDACEAN CRUSTACEANS — TATTERSALL 529 



Genus Lophogaster M. Sars 



Lophogaster M. Sars, 1857, p. 1G0. 

 Ctenomysis Norman, 1862, p. 151. 



Remarks: The genus Lophogaster is so homogenous and its 

 generic characters so clearly defined that it can readily be distinguished 

 from closely related genera of the suborder. On the other hand, the 

 separation of its species has always presented great difficulty to the 

 taxonomist because of the slight differences in their specific characters 

 and of individual variation that may occur. As a result, there has 

 been much confusion in the records of members of this genus in the 

 past. 



Differences between species lie not so much in the general form of 

 the animals as in the degree of development of certain characters such 

 as the length of the various spinous processes, the shape and relative 

 length to breadth of the antenna! scale and the number of denticles on 

 its outer margin, the proportions and armature of the telson, and the 

 amount of tuberculation or spinulation of the integument of the 

 carapace. 



Fage (1942, p. 5) noted that in most species of the genus, noticeable 

 sexual differences occurred in some of these characters. Frequently 

 the rostrum and sometimes other spinous processes became more 

 elongated in larger females than in the males and young individuals. 

 There is also a tendency for the number of spines arming the lateral 

 margins of the telson to be greater in males than in females of the same 

 species and for any tuberculation or spinulation of the carapace to be 

 more pronounced in males. 



Fage (1940, 1942), when reporting on the very rich collections of 

 this genus made by the Dana, noted two characters which proved to 

 be much more constant, and therefore much more useful as taxonomic 

 guides, than those hitherto used. These characters were (1) the form of 

 what he termed the "antennular scale" * (the lamellar prolongation 

 from the inner region of the distal margin of the third segment of the 

 antennular peduncle) and (2) the dorsal profile, in lateral view, of the 

 wings of the carapace together with the size and direction of the 

 posterolateral or alar spines, when these were present. 



Specimens of Lophogaster have been recorded from various localities 

 in all the tropical and warmer temperate waters of the world, including 

 the Mediterranean and the Red Sea. Fage noted that animals show- 

 ing a correspondence in the form of their spinous processes, and 

 in his new characters, sufficient to justify placing them in separate 



1 As this platelike prolongation is in no way homologous with the anti'nnal scale (which is the modified 

 exopod of the antenna), it is perhaps eonfusing to call this structure a "scale." I have therefore used the 

 word "lamina" for it throughout this work. 



