the crinoid hypocrixus. 913 



Summary. 



The two specimens of Hypocrinus schneideri Beyv., described by 

 Beyrich and Rothpletz respectively, are redescribed and refigured. 

 The structui'e of the genus is shown to agree with that of the 

 Devonian family Gasterocomidse, but it is suggested that in this 

 case and in that of ^^ Lecythiocrinus" adamsi the distinctive 

 features may have been independently acquired. 



The holotype of " Hypocrvmis " piriformis Rothpletz is re- 

 described and refigured, and proved to be no Hypocrinus. It is 

 thought to be a highly modified descendant of the Taxocrinida?, 

 by vi^ay of such a genus as Cydonocrinus. The left posterior 

 radial appears to have borne a large arm, but the other arms were 

 more or less atrophied, and the right posterior radial has almost 

 disappeared. 



EXPLANATION OF PLATE XC. 



Hj/pocrinus schneideri Beyr. 



Figs. 1-4 are pliotographs of the holotj-pe, enlarged sliglitlj^ 

 less than 2 diameters. 



Fig. 1. View to show the relations of the periproct, which is the opening nearest 



the observer. 

 Fig. 2. View from above the oral pole, showing the peristome and radial facets. 

 Jig. 3. The cup from the right side: o., oral pole ; a., anal opening or periproct. 



Note the light colour of the dense stereom at the sutures, contrasted 



with the staining of the porous stereom of the general surrace. 

 Pig. 4). The cup from below, with the posterior iuterradius away from the observer. 



Note the sutures between the infrabasals. 

 Fig. 5. A photograph os the peristomial area of the specimen figured by Rothpletz. 



The periproct is at the lower corner of the tigure. X 5 diam. 

 Fig. 6. Micro-photograph of the upper part of one of the basals in the holotype. 



X 7 diam. 



" I£t/2Joci'inus " piriformis Rothpletz. 



Fig. 7. The ground-down base of the holotype, photographed under water, so as to 

 bring out the sutures between the infrabasals and the live axial nerve- 

 canals in those plates (see detailed description on pp. 905, 906). The 

 orientation is as in fig. 4, and approximately opposite to tliat of Roth- 

 pletz, pi. x. f. 23 />. X 4 diam. 



Figs. 8-10. Photographs of the holotype, nat. size. 



Fig. 8. Shows the posterior basal with the protuberant left posterior radial (1. p. R.) 

 above it and the periproct at its right upper corner. 



Fig. 9. View from above the oral pole, showing tlie distorted peristome with the 

 large but obscure facet ol left post. R. to the left, and the anal opening 

 towards the observer. 



Fig. 10. The basal facing the observer is the right anterior. Above it is the peri- 

 stome (o.), with the left post. R. rising up behind it, and with the anal 

 opening (a.) to the left. Note the ornament of growth-lines in the lower 

 part of the cup. 



All the pliotographs were taken by Mr. H. G. Herring, and represent a 

 selection from many attempts upon these diificult subjects. 



\_Note. The following corrections were received too late for insertion in previous 

 sheet : — 



Page 896, line 15 from bottom 1 For Hi/pocrimis miilleri. 

 Page 800, „ 19 „ „ ) Read K. mnUeri. 



EDITOJi.] 



