Revieics — Bather's Crinoidea Of Gotland. 135 



which is built up of a median dorsal row of plain hexagonal plates 

 lying between similar rows of plates folded on their outer sides, and 

 thus it differs hardly at all from the ventral sac of B. ramosissimiis. 

 1'he author failed to find any pores or slits in the ventral sac, but 

 there apjiears to be an anal opening bordered by small plates nearly 

 at the base on the posterior side of the sac (pi. vi. fig. 183). 



The genus Streptocrinus, W. and S. (= Ophiocrinus, Aug., not 

 Salter,), cannot at present be placed in any recognized family. The 

 only known species, S. crotalurus, Ang., sp., is solely represented by 

 mere fragments, amongst which are the curled-up pinnulated arms, 

 supposed at first to be the stems with cirri of a species of Herpeto- 

 crinus. The paii'ed pinnules possess a broad V-shaped ventral 

 groove, covered by quadrangular plates similar to those of the 

 brachials. The author considers that they have arisen as merely 

 processes of the brachials, and they are termed, as already men- 

 tioned, " false " pinnules. 



The important family of the Cyathocrinid^ is defined as Inadu- 

 nata, Fistulata, Dicyclica, with no radianal or tube-plate in the anal 

 area of the dorsal cup ; with the anal x-plate either present in the 

 cnp or raised above it ; with five arms, simple and dichotomous, and 

 with a rather solid tegmen. To Cyathocrinus itself 14 species from 

 Gotland were referred by Angelin, but some of these turn out to be 

 synonyms, and others were not well founded, so that now only 

 9 species remain, and two of these are new forms. In C. acinotubus, 

 Ang., and in some other species of this genus as well, the author 

 describes and figures some very interesting structural features in the 

 ventral covering-plates of the arm ossicles, which exhibit a very 

 elaborate arrangement of their articulating surfaces. Each covering- 

 plate appears, from the exterior, to be divided by a suture, and on 

 the interior there is a small round ossicle. The edges of the ventral 

 groove are also marked olf into concave subcrescentic facets for the 

 articulation of the covering-plates, and each facet has a median notch. 

 The proximal articulating portion of the covering-plates is similarly 

 marked off. These structures are well shown on pi. vii. figs. 2U8- 

 218, 243-247, and pi. viii. figs. 249-250, 254-256. 



The genus Gissocrinus, Aug., is numerously represented in Got- 

 land, and 10 species are described. This genus has generally been 

 considered as differing from Cyathocrinus only in having three 

 instead of five iufrabasals, but the author points out that it is further 

 characterized by the very distinct axial ridging of the cup-plates, 

 the lateral compression of the distal portions of the arms, the 

 elevated or cornice-like rim at the distal ends of the brachials, the 

 strong transverse folding of the plates of the ventral sac, and its 

 length and lateral compression. The covering-plates of the brachials 

 in some species are even more complicated than in Cyathocrinus. In 

 some instances, as in G. typus for example (pi. viii. figs. 273-275), 

 they form such a close-fitting series that it is difiScult to see how the 

 food-grooves can have communicated with the exterior, unless it 

 were at the distal ends of the arms. 



The above desultory notes on the contents of this Part (I.) will, 



