02 DR. p, n. CAEPENTER ON SOME ARCTIC COMATULiE. 



same stage of development, witli tlie first wliorl of cirri just 

 forming ; but I cannot seethe complete correspondence between 

 the two on whiicli he lays so much stress. Sars gave the dimen- 

 sions of his larva as follows : — 



Stem of 49 joints 21 mm. long. 



Head and 18-20 arm-joints .... 4 „ 



His figure also shows the first costals to be nearly square, and 

 the axillary longer than wide, while the cirri are quite rudi- 

 mentary, only just reaching above the basi-radial suture (fig. 8). 

 Now in the Jan Mayen larva one cirrus at least is much better 

 developed, having well-defined joints, and almost reaching up to the 

 level of thie first brachials ; while the costals present characters of 

 much greater maturity, the first being oblong and the axillaries 

 wider than long (PL II. fig. 1). It is altogether more robust than 

 the larva of A. tenella, as the following measurements show : — 



Stem-fragment of 26 joints .... 14 mm. long. 

 Head and 8 arm-joints 4 „ 



This greater robustness at the same developmental stage is, of 

 course, only to be expected if the Jan Mayen larva belongs to 

 A. prolixa, which reaches such a much larger size than A. tenella 

 in the adult condition ; while, as was pointed out on pp. 177-178 

 of the ' Challenger' Report, there is a fallacy in Eischer's argu- 

 ment respecting these Pentacrinoids, which altogether vitiates his 

 conclusions as to the identity of ^. tenella and A. pi'olixa. I am 

 well acquainted with the various developmental stages of ^. tenella, 

 and should certainly not refer the Jan Mayen larva to this 

 species. It is, however, very closely similar to a larva dredged 

 by tlie ' Porcupine ' in the cold area of the Earoe Channel, which 

 I figured in the ' Challenger ' Eeport*. The first costals of this 

 larva are oblong, and the axillaries wider than long ; while its 

 measurements are as follows : — 



Stem-fragment of 30 joints .... 20 mm. long. 

 Head and 10 arm-joints 4 ,, 



This 'Porcupine' larva and that from Jan Mayen undoubtedly 

 belong to the same species. The former is quite difi'erent from 

 the Pentacrinoids o^Antedon tenella and A. Escliricliti, which were 

 dredged in the same locality ; and I was therefore led to refer it 



* Op. cit. pi. xiv. fig. 3. 



