MUSEUM OF COMPARATIVE ZOOLOGY. 177 



Loriol * to establish a new family Bourgueticrinidce, which comprises the 

 two genera just mentioned, together with Batkycrinw and Mesocrintu, a 

 genus recently proposed by myself. De Loriol also includes in it Ilycri- 

 nns of Danielssen and Koren ; but this genus is certainly identical with 

 Bathycrinus, which was founded by Sir Wyville Thomson | on an imma- 

 ture specimen dredged by the " Porcupine " in 2435 fathoms, two hun- 

 dred miles south of Cape Clear. His description J of the larger species^ 

 B. aldrichianus, from the Southern Sea, seems not to have reached the 

 Norwegian naturalists before the publication of their genus Ilycrinus, 

 which was founded on much more developed individuals than that 

 dredged by the " Porcupine." 



Of the four genera included in De Loriol's new family, Bourgueticrinus 

 and Rhizocrinm arc the two most closely allied. The differences between 

 them are greater than was supposed by Sars, owing to his mistake about 

 the basals of the latter type, and may be summarized as follows : — 



Bourgueticrinus. Lower stem-joints not longer than wide ; while one or two at 

 the top of the stem are much longer t'nan those below, and help to form the 

 " summit." Basals usually wider than high. 



Bhizocrinus. Lower stem-joints usually much elongated, two or three times as 

 long as wide. Those just below the calyx are the shortest, often being mere 

 disks. Basals usually much longer than wide, occupying the greater part of 

 the length of the calyx, which expands somewhat from below upwards. 



The last type to be mentioned is the remarkable genus Holopus, about 

 which much information will be found in a communication § by Sir 

 Wyville Thomson to the Royal Society of Edinburgh, in 1877. Since the 

 publication of this paper Sir Wyville made a horizontal section of the 

 cup about two thirds of its height from the base. I was never fortunate 

 enough to learn his own views on the subject, but the appearance of the 

 section leads me to believe that the lower part of the cup is formed by 

 basal plates which project inwards and upwards above the level of the 

 outer edges of the radials, just as in Pentacrinus.\\ 



* Paleont. Franc., he. cit., p. 63. 



t The Depths of the Sea, pp. 450-454, fig. 73 ; and Proc Roy. Soc. Edinb.. YdL 

 VII. pp. 772, 773. 



t " Notice of new Living Grinoida belonging to the Apioerinida?," Journ. Linn. 

 Soc. Zoology, Vol. XIII. pp. 48-51. 



§ " On the Structure and Relations of the Genoa Holopus," Froc. Boy. > B. Edinb., 

 Vol. IX. p. 400. 



II Schliiter (loc. cit., p. 51) is inclined to believe that basals arc present in 

 thulium spilcccense. Like Sir Wyville Thomson, I am unable to differentia* 

 thidium from Holopua, 



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