174 BULLETIN OF THE 



Mr. Agassiz mentions in his dredging letters that he obtained a 

 number of specimens of Rhizocrinus among the Windward Islands in 

 1878-79, and a few specimens in 1880 on the line from Cape Hatteras 

 to St. George's Shoal ; but not having seen any of them, I can say 

 nothing as to the species which they represent. 



In 1869 two examples of this genus were obtained by the "Porcu- 

 pine " off Cape Clear, in 862 fathoms (No. 42), aud were referred at the 

 time to R. lofotensis. On comparing them, however, with some speci- 

 mens of R. rawsoni from off Havana, I find that they really belong to 

 this type, as I had always suspected since reading Pourtales's description 

 of it.* R. raivsoni was also dredged by the "Challenger" in 900 fath- 

 oms among the Azores. It is readily distinguished from R. lofotensis by 

 its more robust appearance and elongated «alyx, which is nearly always 

 constricted at the basiradial suture, instead of widening gradually up- 

 wards, as does that of R. lofotensis. The first radials are much shorter 

 relatively to their width than in R. lofotensis, and the epizygal of the 

 syzygial first brachial is not markedly narrower than the hypozygal as 

 in the latter species. The greater part of the cup is formed by the 

 elongated basals. In the Norwegian variety of R. lofotensis these fuse so 

 very completely that no sutures are usually visible on the exterior of 

 the calyx. This led Sars t and Ludwig J to suggest that the basals of 

 the young Rhizocrinus undergo metamorphosis into a " rosette," as in 

 most Comatula, though this view is not supported by the observations 

 of Pourtales § and myself ; || and the fact that the so-called "enlarged 

 upper stem-joint " of R. lofotensis really consists of the anchylosed basals 

 as originally stated by Mr. Pourtales ^[ for the Caribbean variety is now 

 generally recognized.** The difference in the relative proportions of the 

 two species is seen in the following table, which also shows the sizes of 

 the stem-joints in the examples of R. rawsoni that were dredged by the 

 "Blake," "Challenger," and "Porcupine" respectively, and in Sars's 

 largest specimens of R. lofotensis. 



* Zoological Results of the " Hassler " Expedition, 111. Cat. Mus. Comp. ZooL, No. 

 VIII. pp. 27-31. 



t Memofrea pour servir a la Connaissance ties Crinoi'des Vivants, p. 12. 



\ Morphologische Studien an Echinodennen, Band I. pp. 120-122. 



§ Loc. cit., p. 29. 



|| On some Points in the Anatomy of Pentacrinus and Rhizocrinus. Journ. Anat. 

 and Fhys., Vol. XII. pp. 48-53. 



1 < ontribntiona to the Fauna of the Gulf Stream at great Depths. Bull. Mus. 

 Com].. Zo8l., Vol. I. No. 7, pp. 128-130. 



** Zittel's Handbuch der Palaeontologie. Palaeozologie, Band I. p. 393. 



