MUSEUM OF COMPAKATIVE ZOOLOGY. 1G9 



more recently, its centrodorsal bears quite as many cirrhus sockets 

 as theirs do, or even more. This rather indicates that it is not merely 

 a premature form, as one might be inclined to regard it, owing to the 

 relatively greater length of its arm-joints. 



The peculiarities of Antedon columnaris are almost sufficiently obvious 

 in Fig. 8. I can find no traces on its columnar centrodorsal of any 

 sutures which would indicate its composition out of two or more anchy- 

 losed joints. In fact the alternating arrangement of its cirrhus sockets 

 indicates the improbability of such an anchylosis. They are disposed in 

 five double rows separated by interradial ridges, at the tops of which 

 minute basals are visible, just as in Fenfacrinus asteria. The lower end 

 of the column is somewhat concave, but appears to be completely closed 

 and devoid of any central perforation. The loose arms obtained with 

 the calyx are rather large and massive, and resemble those o{ Atehcrinus 

 in having the ambulacrum close down upon the top of the large muscu- 

 lar bundles. 



In conclusion I may mention that many of the Comatidoe I have ex- 

 amined were the hosts of Myzoslomidce. The Gulf Stream dredgings of 

 1867-G9 yielded these curious parasites at five stations. They were 

 also obtained on the Yucatan Bank, and at two other localities during the 

 "Blake" expedition of 1877-78, and at fourteen stations between Mont- 

 serrat and Grenada in 1878-79. Twenty specimens were dredged at 

 No. 269 (off St. Vincent), where Comatidoe. were very abundant. Captain 

 Cole's haul off" St. Lucia also yielded one specimen, and I found another 

 on the Actinometra sent to the Copenhagen Museum as Antedon Hagenii. 

 The Actinometra brought from Yeddo by Prof. E. S. Morse also furnished 

 an example. All the Myzostomidce have been sent, together with those 

 from the "Challenger" dredgings, to my friend, Prof L. Graff, of Aschaf- 

 fenburg, who has added so much to our knowledge of the European 

 species. 



Published October 1, 1881. 



