REPORT ON THE CRINOIDEA. 357 



joints, the frequent alternation of thick and thin joints in the stem, and the small size of 

 its arms. 



The larger specimen, figured on PI. XL VI., appears to have met wdth an accident since 

 it was drawTi, for it came into my hands in the dry state, having lost its stem and basal 

 ring. The characters of the rays and arms, however, are so essentially similar to those of 

 the smaller individual that I have no hesitation in regarding the two as identical. The 

 characters of the stem as a whole come nearest to those of Metacrinus cingulatus 

 (compare PI. XLI. figs. 1-3, and PI. XLV. figs. 2-6). In both cases there is a continu- 

 ous horizontal ridge round each of the mature internodal joints, but the articular faces 

 are more lobate in Metacrimts cingulatus (PI. XLI. fig. 3) than in Metacrinus moseleyi 

 (PI. XLV. fig. 2). The same is the case with the nodal joints which have more produced 

 angles and consequently deeper cirrus-sockets in Metacrinus moseleyi than in the larger 

 species. The characters of the cup, however, are quite difi"erent in the two types, that of 

 Metacrinus cingulatus being extremely regular in the number of its radials, while in 

 Metacrinus moseleyi there may be as few as three or as many as six. The only other 

 species which resembles it in this respect is the large Metacrinus rotundus ^ from Japan, 

 which has a smooth stem, with much longer internodes. The ten rays of the two indi- 

 viduals of Metacrinus moseleyi are constructed as follows : — 



* One of three joints, the second and the axillary both syzygies. 



* One of four joints, the second and the axillary both syzygies. 

 Three of five joints, the second a syzygy. 



Two of five joints, the second and fourth syzygies. 



One of six joints, the second a syzygy. 



Two of six joints, the second and fourth syzygies. 



The number of primitive joints iu the ray, therefore, before the union of one or more 

 pairs by syzygy, varies from five to eight, just as in other species of Metacrinus. The 

 irregularity which distinguishes Metacrinus moseleyi thus lies rather in the mode of 

 union of the primitive joints to form syzygial pairs than in any excess or defect of their 

 numljer ; though as a general rule there are either five {Metacrinus angulatus) or eight 

 {Metacrinus ivyviUii), and not both t}"pes in the same individual. 



Two very anomalous instances which occur in the dry specimen are marked with an 

 asterisk iu the above list. In the first case the five primitive radials have become 

 reduced to three, owing to the union of the last four into two syzygial pairs. In 

 Metacrinus cmgulatus (PI. XXXIX. fig. l) the fourth primitive joint remains distinct 

 from the axillary to which it is united by muscles, and bears the second pinnule. But 

 on this abnormal ray of Metacrinus moseleyi these two joints are united by syzygy, and 

 as the hjrpozygal of a syzygy never bears a pinnule, the natural condition would have 



' See Trans. Linn. Soc. Lond. (ZooL), ser. 2, vol. ii. p. 437. 



