KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:0 2. 101 



This family is divided into two Series, Dendrocrinites and Scaphiocrinites, according 

 as the arms are simple or pinnulate; it also happens that the genera in the latter Series 

 have all three plates in the anal area. The former Series, with which alone the investigator 

 of Siluria is concerned, may be defined thus. 



Dendrocrinites. 



Dendrocrinidae with non-pinnulate arms, and with from one to three plates in 

 the anal area. 



The genera referred to this series are Merocrinus, Ottawacrinus (il truly Dicyclic), 

 Dendrocrinus, Mastig ocrinus, Homocrinus and Parisocrinus. The genus Bactrocrinus ap- 

 pears to be related to the Euspirocrinidae or to the Cyathocrinida\ The only one of these 

 genera found in Gotland is Homocrinus. 



Homocrinus. 



1852. Homocrinus, Hall, Nat. Hist. N. Y., Palteont. vol. Il, p. 185. 



1859. Poteriocrinus, Hall, pars, Corrected List of N. Y. Fossils {pde Wachsmuth and Springer). 

 1861. Homocrinus, Hall, emend., Nat. Hist, N. Y. Palreont. III, p. 102. 



1H79 and 1886. Homocrinus pars, Waciismutii and Springer, Revision, I, p. 77, and Revision, III, 

 p. 220. 

 non Eichwald, 1859. 



This genus seems to be in a state of considerable eonfusion; and this confusion is 

 due, as in so many other cases, to the fäet that the original diagnosis of the genus con- 

 tained no diagnostic characters, and that the two original species were founded on in- 

 sufficient material. Once more therefore it is our unpleasant duty to discuss the opinions 

 of authors before the facts of nature. 



The name Homocrinus was first used by Prof. J. Hall in 1852 (op. cit.). As 

 Wachsmuth and Springer })ointed out (Rev. I, 77) the clescription that he gave was so 

 indefinite that it would have done for any non-pinnulate dicyclic Inadunate erinoid. The 

 species then referred by Hall to the genus were H. parvus (op. rit., p. 185, Pl. XLI, 

 figs. 1 a, b, c), H. cylindricus {op. cit., p. 186, Pl. XLI, tigs. '2 a, b, c and 3 a, b, c), 

 and two species previously referred by him to Poteriocrinus, viz., P. gracilis and P. alter- 

 natus (Pakpont. N. Y., vol. I, pp. 83, 84). The two latter species have been subsequently 

 referred to Halls own genus, of the same date, Dendrocrinus, and are therefore out of 

 the discussion. Concerning the two former species Wachsmuth and Springer remarked 

 as follows (loc. cit.), »The typical specimens which Hall used for description were most 

 unsatisfactory, that of H. parvus being evidently a very young individual, while those of 

 H. cylindricus are very imperfectly preserved.» There is certainly nothing in the descrip- 

 tion or hgures of H. parvus to show that it is congeneric with H. cylindricus, and it 

 seems very doubtful to what genus it belongs; it is therefore better to ignore this species, 



