MUSEUM OF COMPARATIVE ZOOLOGY. 177 



Loriol * to establish a new family Bourgueticrmida', which comprises the 

 two genera just mentioned, together with Ba(h//crinus and Mesocrinus, a 

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

 7111S of Danielssen and Keren ; but this genus is certainly identical with 

 Batlujcrinufi, which was founded by Sir Wy ville Thomson f on an imma- 

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

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

 B. ahlrichianus, from the Southern Sea, seems not to have x'eached 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 Rhizocrinus are 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 than those below, and help to form the 

 " summit." Basals usually wider than high. 



Rhizocrinus. 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 

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

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

 cup aV)out 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 upwai'ds above the level of the 

 outer edges of the radials, just as in Pentacriuus.^ 



* Paleont. Frang., loc. cif., p. 63. 



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

 VIL PI). 772, 773. 



X " Notice of new Living Crinoids belonging to the ApiocriniJae," Journ. Linn. 

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



§ " On the Structure and Relations of the Genus Holopus" Rroc. Roy. Soc. Edinb., 

 Vol. IX. p. 409. 



II Schliiter {he. cif., p. 51) is inclined to believe that basals are present in Cya- 

 thidium spikccense. Like Sir Wyville Thomson, I am unable to differentiate Cya- 

 thidium from Holopus. 



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