308 



DR. P. n. CARPENTER ON THE 



sides. This is also visible in the lower parts of the brachial 

 ambulacra, which are often entirely closed by an irregular alterna- 

 tion of processes from opposite sides (PI. XXVI. figs. 4, 5). There 

 is, however, no indication either of side-plates or of covering- 

 plates on the pinnule-ambulacra, which are of the usual cha- 

 racter. But isolated portions of the brachial ambulacra effervesce 

 strongly with acid, and the perisome would therefore seem to 

 contain a considerable amount of diffused limestone particles 

 which are not concentrated into definite spicules or plates, as in 

 most other Crinoids. This would partly account for the hardness 

 and leathery character of the perisome on the disk. 



The condition of the disk and the bidistichate rays are the 

 essential points of difference between A. Andersoni and the three 

 existing members of the Eleg cms- gYoxxy. It resembles, but sur- 

 passes them all in the great length of its cirri (PI. XXVII. fig. 8), 

 and also in the length of the first pinnule ; but this pinnule is on 

 the second brachial and not on the second disticbal as in the 

 jEVeyaws-group, while its successors do not decrease slowly in 

 length, but exhibit a sudden and remarkable diminution in size 

 (PL XXVI. fig. 2), that of the third brachial consisting of but 

 half a dozen small joints. The following pinnules increase 

 gradually in length, but never reach any considerable size. 



Another characteristic feature of A. Andersoni is the convex 

 shape of the joints forming the rays and their subdivisions, and 

 also the lateral compression of the arm-joints. Owiug, however, to 

 the rays being so widely separated, there is no trace whatever of 

 that lateral flattening of their bases which is so characteristic of the 

 Uasicurva, S/nnifera, and Granulifera- groups, and occasionally 

 shows itself also in A. elcgans. It is very marked in the fossil 

 A. costata, for which Walther* has recently proposed to restore 

 the generic name Solanocrinus, originally applied to this species 

 by Oddfuss. For he believes that the fossil species which he 

 refers to this genus are devoid of the syzygies in the arms which 

 occur more or less frequently in other Crinoids. He attempts 

 to establish some other characters which would distinguish the 

 genus from Anfedon — an attempt which he would scarcely have 

 made had be been better acquainted both with the literature 

 of the lubject and with the condition of many recent species 



* " L'litorHiicliun^on iihor don Bail tier Crinoidcn, init besonderor Bdriick- 

 Hiclitigung dor Funncii Mil den BolonhofeneV Schiefov und dan Kclheiintr 



Dtaerajkalk," Polieontographica, 1880, I'd. xxxii. p. 17« r ». 



