18 Dr. P. 11. Carpenter on the 



noticed in the ' Challenger ' Eeport there are but nine in 

 which the first two joints beyond each successive axillary are 

 not always united in the same manner as the two costals are. 

 Thus in the three members of the Ekqans-gronp the costals 

 are united by syzygy, while the first two joints after each 

 axillary are articulated. In the six members of the Granu- 

 Ziyera-group the costals and the first two distichals are articu- 

 lated bifascially. Five of the species have the corresponding 

 palmars and brachials united by syzygy, while in the sixth 

 this is replaced by a muscular articulation. 



Among the eighty-four species of Actinometra the four 

 members of the T^/^^^ca-group have a syzygy between the two 

 costals, palmars, postpalmars, and brachials respectively, while 

 the first two distichals are articulated ; and in the seven 

 species of the Ftmh-iata- group the costals and the first pair 

 of distichals are respectively united bifascially, while there 

 is a muscular articulation between the first two joints after 

 the distichal and all subsequent axillaries. The four members 

 of the SteUi'gera-gYOVi\) again have the first two free brachials 

 united by syzygy, while the corresponding joints of all the 

 lower arm-divisions are articulated. 



Excepting in these aberrant forms, therefore, the facts of 

 Crinoid anatomy are in favour of the view that the plates 

 called second and third radials by Mllller really belong to the 

 arms; and so I propose to abandon the use of R in the specific 

 forraulse of the Elegans-, Solaris-, and Ti/pica-gvouTps'^ , and to 

 substitute a c, indicating the costals, just as d stands for 

 distichals and p for palmars. A glance of the illustrative 

 formulae given below, and especially those of Actinometra 

 Solaris and A. paucicirra, will show that this alteration makes 

 them at once more simple and more symmetrical ; and as it 

 seems undesirable to have one c in the formulai to indicate 

 costals and another in the cirrus-notation, as pro])osed by 

 Bell tj 1 pi'opose to use x, y, z for the latter purpose instead 

 of a, i, c. This has the further advantage of enabling us to 

 write a simple 5, and not hr, to indicate the free brachials of 

 the arms. 



* See the Report od the ' Challenger ' Comatuhe, pp. 53, -57, 



t " An Attempt to apply a Method of Formulation to the Species of 



the ComatuUdce , with the Description of a new Species," Proc. Zool. Soc. 



Lond. 1882, p. 531. See also tlie Report on the ' Challenger' Comatula;, 



pp. 43-59. 



