142 THE VOYAGE OF H.M.S. CHALLENGER. 



The armature of the two species may be best appreciated side by side, and formu- 

 lated as below. 



The marginal fringe of the carapace is 



Male, Polyeheles helleri, .... 7-4-5, gradually decreasing. 



Female, Polyeheles helleri, .... 7-4-14, gradually decreasing. 



Female, Pentacheles seulptus, .... 6-3-6, gradually decreasing. 



Median dorsal ridge 



Male, Polyeheles helleri (counting the rostral teeth), . . . 2'1'1"2'1 = 2'2'2. 



Female, Polyeheles helleri (counting the rostral teeth), . . 2 - l'l"2*l = 2"2"2. 



Female, Pentacheles seulptus (counting the rostral teeth), . . 2"1" "2"1 = 2'2 , 2. 



On the inner side of the orbital notch the frontal margin is armed with a small 

 tooth in Pentacheles seulptus, and so in the female of Polyeheles helleri. 



" In front of the cervical suture there is an irregular longitudinal dorso-lateral line 

 of five minute spines ; on each side of and behind these, a single spine on each side on 

 the posterior edge of the cervical suture." The last of these alone is present in the male 

 of Polyeheles helleri, in the female there is, besides, a small tooth on the inner side of 

 the orbital notch, and one or two nearer the median line, but not in a line corresponding 

 with those given in Sidney Smith's plate. 



" Extending from the posterior margin nearly to the cervical suture, there is a sharp 

 sublateral carina parallel to the lateral margin, about a third of the way from it to the 

 median carina and armed with five or six small spines." 



These also exist in Polyeheles helleri, and traverse the line corresponding with the 

 upper edge of the inner wall of the branchial chamber. 



The character of the ophthalmopoda is similar, and the passage in this description 

 (page 137) relating to the translucent appearance of the external tissue of the eye 

 was in type before Smith's remarks on the same were published. I do not mention 

 this to plead for priority of observation, but to demonstrate, from independent sources, 

 how close the relationship between the two animals from antipodal regions really 

 is, and that Mr. Smith's observation supports this opinion. 



Excepting the termination of the fifth pair of pereiopoda in the males there is no 

 structural distinction between the two forms, so far as I can determine, but that of a tooth 

 or two on the outer surface of the carapace, and I think there are few naturalists but 

 must feel that the two specimens, except for the generic feature, might have been classified 

 as belonging to one and the same species, so closely does Polyeheles helleri resemble 

 Pentacheles seulptus. 



