VITT. Cyathocrinua. 213 



Cyathocrinua in Silurian rocks, we now know a consideraLle 

 number of Silurian species that may be referred to this genus. 

 The Limestone Beds d and _/ of Gotland furnish nine species 

 of Cyafhocriniis, as described in a pa])er read before the Royal 

 Swedish Academy of Science on Dec. 9th, 1891 ■^■. The 

 Nia<2;ara Limestone of America contains Cyathocrinus cora^ 

 Hall, C. iraitl-oma, Hall, and C. Van Ilornei, S. A. Miller; 

 but other Silurian species from N. America appear to belong 

 rather to Botryocrinus. The Wenlock Limestone of England 

 lias as yet presented us with only two species, viz. G. acino- 

 tubus, Ang., also found in Gotland [d and _/ ), and a species 

 here described for the first time under the name C. vallafus. 



As shown in the ])a|)er above referred to, the Cyathocrini o^ 

 Gotland fall into three groups. The first of these groups has 

 a stem of moderate widtii, with rather low and alternately 

 ridged columnals and a more or less conical cup. Both our 

 British species come into this group, and the following 

 synopsis shows the main differences between the species of 

 the group : — 



a. Cup with .straii^lit side.'j. 



a. Plates plane, gTanular C. Diuncp. 



b. Plates axially folded aud .striate C. striolatus. 



b. Cup with convexo-concave sides, irregular. 



c. Plates plane ; smooth or pustulate C. visbycensis. 



d. Plates tumid ; smooth or shagreened C. acinotuhus. 



c. Cup with convex sides. 



e. Plates plane ; concentrically ridged and pustulate. . C. vaUatin^. 



There are of conrse many other differences between the 

 species than those shown in the above table, but they can be 

 gathered from the diagnoses. 



CyathocriuKS acinofi(hfs, Ang. 

 (PI. XIIL figs. 1-13.) 



1878. Cyathocrimis acinotuhus, Angelin, Iconographia, p. 22, pi. xx. 



fig. 5. 

 1878. Cyathocrinus ahdacens (pars), Angelin, Iconographia, pi. iv. 



fig. 6 a. 

 1873. CyatJiocrinm (sp. 6) monile, nom. nud., Salter, ' Catalogue of 



Cambrian and Silurian Fossils &c.,' Cambridge, p. 123. 



* F. A. Bather, " The Crinoidea of Gotland, Part I.,'' Kgl. Svenska 

 Yet.-Akad. Ilandl. Bd. xxiv. no. 8. In the press. 



