KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 25. N:0 2. 39 



British Association rule 11 1 ). »A name inay be changed when it iraplies a false proposi- 

 tion which is likely to propagate important errors». That important errors were so pro- 

 pagated we have already seen. 



But more important is the fact that Messrs. Wachsmuth and Springer rejected 

 Hall's genus on two separate occasions, and, so far as tbey used »Myelodactylus» at all, 

 applied the name provisionally to Angelixs M. heterocrinus. The observations of Messrs. 

 Nicholson and Etheridge, who, on their own showing, had not examined Salter's type- 

 specimen, hardly outweigh those of our eminent American authorities. 



The name Ophiocrinus proposed by Charlesworth had previously been used by 

 Salter for a fossil Crinoid from South Africa; its value therefore needs no discussion. 



The name Herpetocrinus is next on the list. Salter's description of the genus was 

 morphologically correct; it is moreover possible to recognise his type-species. His name 

 must therefore be accepted. 



(2) Salters description of Herpetocrinus is as follows. — »A minute cup, all but 

 obsolete, and with dichotomous narrow arms, branched like those of Homoerinus, Hall. 

 This is set on a narrow cylindrical suberect stem, which soon however becomes com- 

 pressed, then hollowed on one side, and bears close set auxiliary arms to the lowest part, 

 so far as observed. The stems coiled up like an adder resemble arms of crinoids rather 

 than stems». Type H. Fletcheri. 



This is sufficiently diagnostic, but does not afford much information as to the sys- 

 tematic position of the genus. The genus, as we have seen, has been variously referred 

 to the Taxocrinida? and the Cyathocrinidaj; and has even been placed in a separate class 

 of Echinoderms. The knowledge acquired by an examination of Salter's type-specimen 

 (a'384 Cambridge Museum), of specimens belonging to Mr Hollier of Dudlev, and of a 

 specimen in the British Museum (47,859), all belonging to H. Fletcheri, led me in April 

 1890 2 ) to ally the genus with Ectenocrinus. In May of the same year 3 ) I placed the 

 genus with a (?) in Fam. Dendrocrinida>, Series Dendrocrinites. 



The evidence of the British Museum specimen (47,859) and of the Stockholm spe- 

 cimens a and k at last enables me to dvaw up the following 



Einended diagnosis. 



BB 5, irregular in size and }x>siition. RR 5, all (?) except 1. post, R divided hori- 

 zontally. Arms simple, dichotomous. .v rests on left upper slope of r. post. R' and 

 partly abuts on 1. post, R and r. post. R s . Ventral tube long, narrow. Stem in proximal 

 region evolute, more or less circular in section; in distal involute, compressed or sub- 

 crescentic in section, with two rows of cirri varying in arrangement. 



The above diagnosis and tigs. 25, 26, 37 and 38 sufficiently indicale that Herpeto- 

 crinus must be referred to the Heterocrinidae, and that it is inöst closely allied to the 

 genus Heterocrinus. 



') Rep. Brit. Assoc. for 18G5, p. 34; London, 1866. 

 2 ) Ann. Mag. Nat. Hist., ser. 6, vol. V, p. 333, note 7. 

 ») Op. rit., p. 384. 



