224 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



Mortcnsen's station 9, although in garrettiana the centrodorsal is not quite so long, and 

 the interradial spares are not quite so hroad; the articular faces of the radials in bocki 

 are the same as those in garrettiana. The cirri have the same number of segments in 

 both, and the single cirrus that remains in the type specimen of garrettiana agrees with 

 the immature cirrus shown in Gislen's photograph extending up into the arms. The 

 form of the ossicles of the division scries and of the brachials is the same in both, as is 

 the carination, the production of the distal ends of the earlier brachials, and the smooth- 

 ness of the outer portions of the arms. 



Features that might seem to indicate that bocki is not the same as garrettiana are : 

 In garrettiana the opposing spine is single, not forked; but the single cirrus present is of 

 the immature type, tapering in the distal portion, and the short blunt opposing spine 

 and terminal claw do not have the normal glassy texture; single opposing spines are not 

 infrequent in species in which the opposing spine is normally or usually forked. In 

 garrettiana the ends of the basal rays are large and prominent tubercles whereas they 

 are not visible in bocki; that is simply an indication of immaturity, the basal rays being 

 commonly very large in immature individuals of the species of Charitometridae. 

 In garrettiana the radials are wholly visible as narrow bands, in bocki mainly concealed ; 

 this also indicates immaturity. In the type specimen of garrettiana there are only 1 1 

 arms, and the single IIBr series and the arms borne by it are not of full size; this is 

 evidently the commencement of adolescent autotomy and indicates that fully mature 

 individuals have more than 10 arms; one of Gisl6n's specimens of bocki has 14 arms. In 

 garrettiana the arms are longer than in bocki — 65 mm. as contrasted with 60 mm.; in 

 individuals with 10 arms the arms are always longer than in those of the same species 

 with 20 arms; the arm length of garrettiana is the distance from the apex of the cen- 

 trodorsal to the arm tip — that is, half the diameter of the circle made by the outstretched 

 arms; in bocki the arm length is presumably the length of the arms from the last axillary; 

 measured on this basis the arm length of garrettiana would be the same as that of bocki, 

 60 mm. The proximal pinnules of garrettiana are longer than those of bocki with more 

 segments; in garrettiana Pi is 6 mm. long with 20 segments, in bocki 3.5-5 mm. long with 

 13-15 segments; in garrettiana P 2 is 5.5 mm. long with 17 segments, in bocki 4.5-5 mm. 

 long with 12-14 segments; in garrettiana P 3 is 5.5 mm. long with 13 segments, in bocki 

 4-^.7 mm. long with 10-11 segments; these differences are slight and do not affect the 

 relative proportions of the pinnules; they are probably due to the fact that the pinnules 

 of garrettiana were measured on an arm arising from a IBr axillary whereas those of 

 bocki were measured on an arm from a IIBr axillary. In the genital pinnules of 

 garrettiana the third and fourth segments are often abruptly larger than those following 

 and flattened; but they are not broader than those preceding and do not have produced 

 lateral borders as in bocki; this is probably an indication of immaturity; the expansion 

 of the genital pinnules is a very variable feature in most of the Charitometridae except 

 for the 10-armed species. In garrettiana the distal pinnules are 5 mm. long with 13-14 

 segments, in bocki 4 mm. long with 11 segments; this difference may well be duo to 

 the fact that in garrettiana they were measured on an arm from a IBr axillary, in bocki 

 on an arm from a IIBr axillary. 



In balancing these correspondences and differences it appears that the former are 

 fundamental, and taken together could scarcely be assumed to occur in two different 

 species, while the latter are all of minor significance and are explainable on the basis 



