168 BULLETIN OF THE 



taining the genus Cainocrinus Forbes, which has recently been resusci- 

 tated by De Loriol.* The distinguished Swiss paleontologist describes 

 the basals of Cainocrinus as in contact with one another all round the 

 calyx, so as to form a complete ring, while those of Pentacrinus are small 

 and not contiguous externally, as shown in Miller's figure of P. caput- 

 medusce {asteria Linn.).f So far as the fossil species are concerned this 

 certainly does appear to be a constant difference, but it is by no means 

 so in the recent ones and in Jfetacrinus. The unique specimen of P. 

 maclearanus } has a closed basal ring, and so have all the examples of 

 P. wyviUe-thomsoni that I have seen, though one or more of the basals 

 occasionally fail to meet their fellows. But in P. naresianus there ap- 

 pears to be no constancy whatever in this respect. Some individuals of 

 this species have a closed basal ring. But in others the basals are 

 comparatively small and the radials are prolonged slightly downwards 

 over the upper stem-joints. A few exhibit both conditions, some of the 

 basals meeting their fellows, while the rest are separated by the down- 

 ward projecting radials. The same variation, though in a less degree, 

 occurs in P. mulleri. But it is in P. decorus that the most remarkable 

 variation occurs in the size of the basals. They are sometimes smaller 

 than those of P. asteria, and scarcely more conspicuous than the inter- 

 radial ridges on the stem beneath them ; or they may be large trian- 

 gular knobs standing out prominently from the general plane of the 

 calyx, and meeting one another laterally by their extended lower angles ; 

 or they may present any intermediate condition between these two. 



The following brief descriptions of the Caribbean species of Penta- 

 crinus are not to be considered as complete specific diagnoses. These 

 will appear, together with the synonymy, in my final report. 



P. asteria Linn. sp. 



Stem robust, reaching 6 or 7 mm. in diameter, with 13-21 (usually 15-18) 

 internodal joints. Cirrus-sockets widely oval, and occupy nearly the whole 

 height of the nodal joint. The hypozygal joints rarely modified, and then very 

 slightly so. 



Cirri reaching 70 mm. in length and composed of 50 stout joints. I. 

 limit of the interarticular pores from the ninth to the twelfth node. The two 

 outer radials united by syzygy. The ray-divisions somewhat irregular. Pri- 

 mary arms of 2-6 (diatichal) joints ; secondary arms of 4-10 (palmar) joints, 



* MonograpLio dea Crinoidee fossilcs dc la Suisse, (Geneva, 1877-79,) p. ill. 



t A Natural History of the Crinoidet, (Bristol, 18S1.J p. Si, PL II. tig. 9. 

 J The Atlantic, Vol. II. p. 124, fig. 31. 



