KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:0 2. 



25 



posterior interradius, and this is fixed by the plate marked ar, which is either the anal x 

 or the proximal plate of the tube. The azygous plate (Az) is thus seen to be a true rädi- 

 anal (El): it partly supports the small r. post. R and r. ant. R, and rests on the truncated 

 r. post. B. 



These ehanges are of great importanee, for they bring Pisocrinus into harmony with 

 the rest of the Monocyelica, with which under prévious terminologies it certainly did not 

 agree. Triacrinus (text-fig. 3) having, so far as the radials are concerned, the same 



Fig. 1. Uissection of Pisocrinus: The plates named 

 according to Wachsmuth and Springek. The asterisk 

 represents the supposed position of the anal interradius. 



<y 



Fig. 2. Dissection of Pisocrinus: The plates named 



according to the views of the present 



paper. 



This dissection is made from a specimen of Pisocrinus pilula from Dudley in the Britisfa Museum: No. 57348. 



1.1 



Wp T.p.VWr.a LlV-V 



Fijf. 3. Dissection of Triacrinus. 



Fig. 4. Dissection of Symbathocrinus 



A-Anus 

 länt I post*- — V post ränt Ant 



<G>> (£) <2>? (g) (g) 



Fig. 5. Dissection of Haplocrinus. 



länt 



post 



r. post 



8o 



ränt Ant 



<8> <& ^ 



Fig. C. Dissection of Heterocrinus. 



structure, would have the same terminology, and this is n<>\\ seen to resemble Symbatho- 

 crinus in the position of its basals (text-fig. 4). It is to be noted that in 1886 (op. cit.) 

 Wachsmuth and Springer ealled the plate in Symbathocrinus marked x an »anal», and 

 said that it gupported the proximal plate of the ventral tube. Ndw also we can compare 

 Pisocrinus with Haplocrinus (text-tig. 5). This genus only differs from Pisocrinus in the 

 presence of an infer-radial in the left and right anterior rays, and in the absenee of a 



K. Sv. Vet. Akad. Handl. Baid. 25. N:o 2. 4 



