*10 PROCEEDINGS OF THE ACADEMY OP [1886. 



Grotalocrinus was established by Austin in 1843 (Ann. and 

 Mag. Nat. Hist., p. 198), for the reception of a single species, 

 which was described by J. S. Miller, in 1821, as Gyathocrinus 

 rugosus, from a calyx without the arms. He had previously 

 used the name Grotalocrinites rugosus (1842, Ann. and Mag., 

 vol. X, p. 109), in his list of the class Pinnastella, and he referred 

 it to the Marsiqnocrinoidea. His original definition of the genus 

 is as follows : 



" Dorsocentral plates, 5 ; first series of perisomic plates, 5 ; 

 second series, 5. On the latter are a series of wedge-shaped 

 plates, which bear the rays ; the exact number of these plates is 

 unascertained. Column with a pentapetalous perforation." 



" C. rugosus. The plates surrounding the body agree with the 

 generic characters. Rays numerous, probably amounting to one 

 hundred. Column composed of thin joints, articulating into 

 each other by radiating strife. The columnar canal is penta- 

 petalous. The raj's are remarkabl}- small m proportion to the 

 size of the animal." 



McCoy, in 1854 (Brit. Pal. Foss.,p. 54),redescribed the genus, 

 but gave little additional information regarding it. He men- 

 tions the presence of an interradial plate in the " second peri- 

 somic row," and saj'S that above, and alternating with the 

 primary radials, are five large pentagonal secondary radials 

 (scapulae), completing the cup, on each of which rests a series of 

 small pentagonal plates, supporting for the width of each plate 

 a large number (? 15 or 16) of very slender long ra3's. Accord- 

 ing to McCoy, the genus "differs from Gyathocrinus in the vast 

 number of its rays." 



Hisinger (Leth. Suec. Supp., II, p. 6) described under the name 

 Gyathocrinus pulcher a specimen without arms which afterwards 

 proved to be of this genus. 



Johannes Miiller was the first to call attention to the remark- 

 able characters of this type exhibited in the brachial parts. In 

 1853 (Abh. Ak. Wiss. Berlin, p. 187, et seq.), he described, under 

 the head of " Crinoiden mit netzfdrmigen Handen," some speci- 

 mens from Gothland in which the arm structure was well shown. 

 He says he could not identify Hi singer's species because his 

 figure was too imperfect, although he thinks it may have belonged 

 to the same group. He also says that a specimen with arms and 

 branches somewhat resembling the net-form had been obtained 



