MUSEUM OF COMPARATIVE ZOOLOGY. 165 



second brachial, and a small stump on the third. Neither the 4th nor 

 the 5th joint has a pinnule at all, but there are small ones on the 6th 

 and 7th joints, and a larger one on the 8th, which was probably the 

 first pinnule to appear at all. 



I have sometimes found that the different arms of the same young 

 individual have reached different stages of development. Thus, in a 

 young Antedon from station 232, one arm has large pinnules on the 2d 

 and 16th joints, smaller ones on the 3d to the 6th, and mere stumps on 

 the rest of the intervening joints. On other arms, however, there are no 

 pinnules at all between the 4th and the 15th joints. Again, in a young 

 Ant. phalangium from the Mediterranean, some arms have no pinnules 

 at all between the 2d and 10th joints ; while in one arm there are 

 pinnules on 2, 4, 6, and 10, but none on 3, 5, 7, 8, or 9. This would 

 seem to show that, when the basal pinnules of this species do begin 

 to appear, the first-comers are those borne by the even-numbered joints 

 on the outer side of the arm. 



Hence, whatever be the order of succession of these basal pinnules 

 inter se, there is good reason to believe that their late appearance as a 

 whole is a marked developmental character among the Comahdce. This 

 is a point of some importance, as will be seen immediately. 



During the Gulf Stream Expedition of 1869, Mr. Pourtales dredged 

 two small ten-armed Comatulte iu 450 fathoms, off Cojima, on the coast 

 of Cuba. They were described by him under the name of Antedon 

 cube?isis ;* but the description given by him only applies to the larger 

 and more perfect specimen, which differs considerably from the smaller 

 and much mutilated one. Mr. Pourtales seems to have recognized that 

 the two were different, for in his description f of the Criuoids obtained 

 by the " Blake " Expedition of 1877-78, he wrote as follows : — " To this 

 species (i. e. A7it. cuhensis) I refer provisionally two specimens very much 

 mutilated, having lost the cirrlii and the arms, differing somewhat from 

 my type specimen, but possibly the differences may be due to age." 

 He then described a specimen dredged at Station 43, in 339 fathoms 

 (to which I shall refer directly), and added that a smaller, equally 

 mutilated one had been previously dredged by himself in 450 fathoms, 

 near Havana (Fig. 7). 



These two specimens are quite different from the type of ^n^. cuhensis. 

 Not only are the first radials visible and the second but little shorter 

 than broad, as was mentioned by Mr. Pourtales, but the first radials are 



* Bull. Mus. Comp. Zool., Vol. I. No. 11, p. 356. 

 ■t Ibid., Vol. V. No. 9, pp. 214, 215. 



