KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:0 2. 23 



its Literature; but, besides this, the discovery of anal structures compels an alteration 

 of the previous terminology. 



L. de Koninck (op. cit.) fonnded the genus in 1858 on the evidenee of three dorsal 

 cups. So far as this material permitted, his description was correct; but the figures appear 

 to be very bad. The two specimens figured were said to come from the collection of Mr. 

 John Gray of Hagley, but, as they do not seem to have found their way, with the larger 

 part of the collection, to the British Museum, I have been unable to compare tliem with 

 the figures. There can, however, be no doubt but that the basals are quite incorrectly 

 drawn in both plate and woodcut, and that the views of the ventral surface given in figs. 

 11 and 13 are largely imaginary. The »more decided» »groove» »on the anal side» no doubt 

 exists, but not in the posterior interradius of de Koninck, for that is now seen to be the 

 right posterior interradius. 



The specimens of Pisocrinus described by C. Ferd. Römer in 1860 (op. cit.) as 

 Synbathocrinus tennesseensis were not well enough preserved to advance our knowledge. 



3. W. Salter in 1873 l ) mentioned that »long tentacular arms» occurred in some 

 specimens; he placed the genus, however, with the Cystidea. 



K. A. Miller, writing in 1878 2 ), obviously without having seen Angelin's Icono- 

 graphia, adds that »one of the arm-plates possesses a very wide and deep ambulacra] furrow 

 for so small a plate», and that »the column is small and round». Mr. Miller saw that 

 the American species differed in the strueture of the base from the figures at least of the 

 European species, and he was the first to give an adequate description of that strueture. 



Angelin (op. cit.) in 1878 figured a specimen with arms, and described the stera as 

 cylindrical, coraposed of sraooth, simple and rather long ossicles, and with a central canal. 

 In his generic diagnosis occur the words »interdigitalia nulla 1. interdum unicum», and 

 under P. pocillum »Interradiale oblonguhim, sexangulum». I take it that both these sen- 

 tenecs refer to the plate that is represented, though rather incorrectly, as partlv ludden 

 by the arms in Tab. IV, fig. 3 a\ these obseure references to it escaped the observation 

 of subsequent writers. Although the unpublished diagrams of Angelin show that he 

 understood the composition of the base, and although Tab. IV, fig. 1 e gives a representa- 

 tion of the basals that mav pass muster, his other figures are either useless in this respect 

 or, as fig. 2 I>, more incorrect than de Koxincks. We cannot therefore be härd on Mr. 

 S. A. Miller for having, in his subsequent writings, ignored the resemblance of Angelins 

 Tab. IV, fig. 1 e to the base of his own P. gemmiformis. 



Dr. E. N. S. RiNGUEBERG (op. rit.) threw no fnrther light on the strueture of the 

 genus, when in 1884 he described two species under the names Triacrinus pyriformis and 

 T. globosus. Apparently he did not intend to refer thein to the Triacrinus of Minister, 

 and, as he compared them with Hybocrinus and not with Pisocrinus, his institution of a 

 new genus was probably due rather to inadvertence than intention. 



The description given by Messrs Wachsmuth and Springer in 1886 (Rev. III, 172 — 

 174, Proc. pp. 96 — 98) was good so far as it went. They stated that the column had a 



*) Cat. Camb. and Sil. Fösa. p. T28; Cambridge. 



'-) Jonrn. Cincinnati Soo. Nat. Ilist., July, 1 8 7 'J . pp. 10, 11. 



