80 DE. W. E. COLLINGE ON THE 



it is either finely granulated or almost smooth, whereas in all the specimens 

 of 1. phosphorea that I have seen there are large lateral and median tubercles. 

 Harger states, "the body, especially of the young, is rough and tubercular 

 along the median line and often, also, laterally. Older specimens are much 

 smoother, losing their large median tubercles, but never becoming as smooth 

 as in" /. baltica. I have seen no examples measuring more than 22 mm. in 

 length, and in all of these both the lateral and median tubercles are quite 

 prominent. 



A comparison of Sars's figures (22, pi. 34. fig. 1) or those given by myself 

 (12 a, pi. 5. tigs. 48-58) of I. granulosa, with those given by Harger (13, pi. 5. 

 figs. 27-29) of/, phosphorea, at once show the difference in the form of the 

 terminal segment of the metasome, the coxal plates of the mesosome, &c. 



In the form of the cephalon (PI. 8. fig. 16) the differences from 1. granu- 

 losa are very marked, and are at once apparent in the width and the deep 

 transverse groove, anterior to the posterior margin. The eyes are larger and 

 situated more anteriorly, whilst the lateral margins posterior to the eyes 

 curve inwards. 



The antennule (PI. 8. fig. 17) is shorter and more robust in this species 

 than in I. granulosa, as also the antenna (fig. 18). 



In I. granulosa I have described (12 a) the coxal plates of the mesosome as 

 occupying the anterior two-thirds of the lateral margin of the second seg- 

 ment, the third rather more, and the remainder the whole of the lateral 

 margins, increasing in breadth from the fourth to the seventh segments. 

 Sars (22) speaks of them as being "comparatively small." 



In I. phosphorea, whilst occupying approximately the same proportion of 

 each segment, they are slightly wider, the external margin being more 

 expanded, so that those of the second, third, and fourth segments are 

 roughlv triangular, the apex of the triangle being rounded. Those on the 

 fifth, sixth, and seventh segments have a sloping margin from the anterior to 

 the posterior angle, whereas in 7. granulosa the margins are almost truncate. 



Harger (13) remarks that young specimens resemble the young of I. irro- 

 rata (— baltica), but that they can be distinguished by the coxal plates of the 

 second and third mesosomatic segments, which do not occupy the whole of 

 the posterior border of the segment. I have compared examples oi I. phos- 

 p>horea of from 10 to IT) mm. in length with similar sized specimens of 

 I. baltica, but I must confess that I fail to note any resemblance between the 

 two, the general shape and coloration at once serving to separate them. 



Although Harger examined large numbers of specimens from twenty 

 different localities, ranging from the New England coast northwards to 

 Halifax, Nova Scotia, and the Gulf of St. Lawrence, and southwards as far 

 as Cape Cod, he never observed a striped pattern of coloration, so common 

 jn I. baltica, with which species it was found associated, the colour being 



