MARINE ISOPODA OF NEW ENGLAND, ETC. 345 



lamella at the apex and very obliquely truncated. It is minutely serru- 

 late toward the tip on the side opposite the laiDella. 



The males of this species sometimes attain a length of 30""" to 38°"", 

 with a breadth of 8™™ to 9°*™ but the females are smaller, rarely, if ever, 

 exceeding 20™"" in length, with a breadth of ({.a™"", and are found witii 

 eggs when not over 7.5""» in length. The color varies greatly. Fre- 

 quently it is of a nearly uniform light or dark green, or brownish with. 

 minute blackish i)nnctations. It is often longitudinally striped with 

 light color, or nearly white on a dark background, and the stripes may 

 be marginal only, or accompanied, especially in the males, by a median 

 dorsal stripe. More rarely the colors are arranged transversely in bands 

 or blotches, and specimens thus marked are easily mistaken for the 

 next species. The females are usually darker than the males, and often 

 with a light lateral stripe, which may be very narrow or broken into a 

 series of blotches. 



A comparison of specimens from both si<les of the Atlantic does not 

 seem to furnish any characters by which to separate this species 

 from the common European form, J. tricuspidata Desm., and as 

 Say's trivial name has priority I have adopted it. I. tridentata Kathke 

 appears to be the same species, but I. tridentata Latreille* is de- 

 scribed by that author as having antennae as long as the body; fur. 

 ther, Desmarest, just before his original description of I. tricuspidata 

 says : " M. Latreille fait observer que cette idotee [I. entomon] est bien 

 differente de celle que M. Leach a decrite sous le meme nom, * * * » 

 cette derniere qu'il nomme Idotee tricuspide," i&c. It would not there- 

 fore appear that Latreille was at that time aware that this species 

 had a name, much less that he had himself named it I. tridentata. 

 Again, in his Cours d' Entomologie, where he copies figures, doubtless of 

 this species, fi'om Savigny's Egypt, he applies to them the name Idotea 

 {pelagica ?), not recognizing them as his own species. Bate and Westwood 

 quote I. tridentata Latreille as a synonym of I. tricuspidata Desm., and 

 their quotation t appears intended to refer to a work nearly twenty years 

 older than that of Desmarest. They do not, however, give their reasons 

 for deviating from the ordinary rules of priority, but, perhaps, con- 

 sidered as sufficient the authority of Edwards, who does the same thing. 

 Edwards' description of I. tricuspidata Desm. contains, moreover, an 

 evident error, the species being placed in a section of the genus which he 

 thus describes : "§ 2 Especes dont I'abdomen se compose de trois articles 

 parfaitement distincts (le second ^tant compos6 de deux anneux sondes 

 ensemble sur le milieu du dos, mais separes par une scissm^e sur les 

 c6t6s)." I. irrorata is included in the same section, but under a sub- 

 section, thus correctly characterized : "aa Le second article de I'abdo- 

 men simple ; le troisi^me offrant pres de sa base une fissure de chaque 



*Geu. Crust, et Ins., tome i, p. 64, 180G. 



tBrit. Sess. Crust., vol. ii, p. 380. The quotation reads, "Idotea tridentata Latreille, 

 Con. Crust, et Ins. 1, p. 64," aud was doubtless intended for Gen. Crust, et Ins., 

 [tome] i, p. 64, [1806]. 



