UINTACRINUS : ITS STEUCTUKE AND RELATIONS. 61 



side. They are not at all of uniform size, but vary all the way from 6 mm. 

 to 37 mm. in width, in about the following proportions numerically : — 



Under 12 mm 150 specimens. 



Between 12 and 25 mm. . . . 350 " 



From 25 to 37 mm 50 " 



Hence the difference in size between these and the specimens from 

 Locality No. 1 is not constant. The largest from Locality No. 2 are larger 

 than the smallest from Locality No. 1 ; but the prevailing size is far below 

 that of the specimens from the latter locality. By far the greater number 

 — 75 per cent at least — are lying with the base exposed, showing that 

 they were clinging close together by the arms ; but of these at least 80 per 

 cent have had the basal plates rubbed off, either by weathering or too 

 severe use of the brush in cleaning. The reason why so many of them have 

 the base exposed is no doubt their small size and the shortness of their 

 arms, by which, in clinging together, the calices were drawn up and held 

 closely against the exterior of the floating mass. The arms were in no 

 case visible to the extremities, but in the smaller specimens were prob- 

 ably not over 10 cm. in length. A large majority of this colony belong 

 to Form D. Out of 99 specimens in which the base is distinguishable, 

 there are : — 



Monocyclic 24 



Dicyclic 75 



As at Locality No. 1, the difference in this respect does not appear 

 to be correlated with any other. Some of the smallest are monocyclic 

 and some of the largest dicyclic, and vice versa. 



Many of these specimens were very small Crinoids. Allowing for the 

 flattening, the smallest of them in life was only about 4 mm. in diameter 

 at the widest part of the calyx, or about the size of an average Pisocriniis ; 

 whereas a large adult from Locality No. 1 was 50 mm., or two inches, in 

 diameter in life. 



The Crinoids of this colony have superficially an aspect somewhat 

 different from those of the other localities. This is partly due to the fact 

 that the brachials are here proportionally more prominent, and the inter- 

 brachial areas less conspicuous ; and also that the basal and radial circlets 

 are proportionally larger in the small ones. An average of a number of 



