ORAL APPENDAGES OF MARINE ISOPODA. 79 



margin, it slopes outwardly, becoming wide at tbe base. There are a number 

 of setose spines on the anterior margin. The epipodite is slightly narrower 

 than the basipodite. It extends forward slightly beyond the anterior outer 

 margin of the second joint of the palp and becomes a little narrower towards 

 its apical margin. 



10. Idotea phosphorea, Harger. (PI. 7. figs. 16-18 : PI. 8. figs. 19-23.) 



Idotea pkosphorea, Harger with Yen-ill, Rept. U.S. Comms. F. & F. 1873, pt. I. 



p. 569; Harger, ibid. 1880, pt. yi. p. 347, pi. 5. figs. 27-29. 

 Idotea marina, var. pkosphorea, Miers, Journ. Linn. Soc, Zool. vol. xvi. (1881) p. 81. 

 Idothea pkosphorea, Richardson, Bull. U.S. Nat. Mus. 1905, p. 367, figs. 398. 399. 



Considerable difference of opinion exists amongst carcinologists as to the 

 specific identity of this species. It was described by Harger in 1873, and in 

 1880 he gave figures of the animal, the antenna, the maxillipede, the first 

 two walking limbs, the second metasomatic appendage, and the uropod. The 

 original description is as follows : — 



"The head is narrowed behind. The eyes are of moderate size. The 

 flagellum of the antennae is shorter than the peduncle, and consists of about 

 ten to fourteen segments. Tbe maxillipeds have the external lamella broader 

 than in the preceding species [/. baltica], with its inner margin straight and 

 its outer margin curving pretty regularly to a slightly attenuated tip. 



"The epimera of the second, third, and fourth pairs are rounded behind, 

 and those of the last three pairs are less acute than in I. baltica *. 



" Pleon ovate, a little constricted near the middle and pointed, its three 

 proximal segments rather less acute than in the preceding species. The 

 basal plate of the operculum tapers towards the end, and the terminal plate 

 is triangular, a little longer than broad. The stylet on the second pair of 

 pleopods in the nude is slender, nearly straight, surpasses the lamella to 

 which it is attached, and is obliquely truncate. 



" Length 25 mm. ; breadth 7 mm." 



Miers regarded this species as a variety of J. baltica (Pallas), and remarks : 

 "There appears to be no sufficient reason to distinguish Idotea granulosa of 

 Katbke .... from the American J. pliosphorea."" 



Whilst I . phosphorea is no doubt closely related to I. granulosa, Katbke, 

 which is now regarded as a valid species, I am of opinion that ihere are 

 sufficient well-defined structural characters which clearly separate it from 

 this latter species. Of these, the most important are, tbe form of tbe 

 cephalon, the coxal plates of the mesosome, and the form of the metasome. 

 In addition, the autennules, tbe antennas, the first maxillae, and the maxilli- 

 pedes also exhibit differences. Finally, in all the specimens of /. granulosa 

 that I have examined the dorsal surface of the body never shows tubercles ■ 



* Termed /. irrorata by Harger. 



