18 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



series being of 2 ossicles. This refers to the present species, although Carpenter did 

 not mention it by name. 



In a paper on the comatulids of the Mergui Archipelago collected by Dr. John 

 Anderson, Superintendent of the Indian Museum, Calcutta, published in 1889. 

 Carpenter described and figured Antedon andersoni. 



Carpenter said that this is a fine species that may be referred for the present 

 to the Elegans group, though it differs from the three members of the group (Zygometra 

 microdiscus, Z. elegans, and Z. comata) which are at present known in certain essential 

 characters. If other species resembling it should eventually be discovered, he said, 

 it may be useful to establish a second group in Series I of the Antedon species, and to 

 call it the Andersoni group. He noted that the three existing members of the Elegans 

 group all have the IIBr series 4(3+4), and have a well-plated disk, whereas in Antedon 

 andersoni the IIBr series are 2, and the disk has nothing like the large plates covering 

 the interpalmar areas that occur in Antedon multiradiata, A. elegans, and A. micro- 

 discus. But on the other hand it is veiy tough and leathery, and the ambulacral 

 grooves are more or less completely closed by the approximation of their sides. This 

 is also visible in the lower parts of the brachial ambulacra, which are often entirely 

 closed by an irregular alternation of processes from opposite sides. There is, however, 

 no indication either of side plates or of covering plates on the pinnule ambulacra, 

 which are of the usual character. 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. 



Carpenter remarked that the condition of the disk and the bidistichate rays 

 (the occurrence of IIBr series of 2 instead of 4 [3 +4]) are the essential points of differ- 

 ence between A. andersoni and the three existingfmembers of the Elegans group. It 

 resembles but surpasses them all in the great length of its cirri, and also in the length 

 of the first pinnule; but this pinnule is on the second brachial and not on the IIBrj 

 as in the Elegans group, while its successors do not decrease slowly in length, but 

 exhibit a sudden and remarkable diminution in size, that of the third brachial con- 

 sisting of but half a dozen small segments. The following pinnules increase gradually 

 in length, but never reach any considerable size. 



Carpenter noted that another characteristic feature of A, andersoni is the convex 

 shape of the joints forming the rays and their subdivisions, and also the lateral com- 

 pression of the brachials. Owing, however, to the rays being so widely separated 

 there is no trace whatever of the lateral flattening of their bases which is so charac- 

 teristic of the Basicurva, Spinifera, and Granulifera groups (that is, the species of 

 Charitometridae and Thalassometridae) and occasionally shows itself also in A. 

 elegans. He said that this is very marked in the fossil Antedon costata for which 

 Walther had recently proposed to restore the generic name Solanocrinus, originally 

 applied to this species by Goldfuss; 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 Solanocrinus from Antedon an attempt which, Carpenter said, he 

 would scarcely have made had he been better acquainted both with the literature of 



