REPORT ON THE CRINOIDEA, Paykel 
this type really are different from those of other Pentacrinide, has re-established the genus 
Balanocrinus wpon them. The five sectors of each more or less circular face have no 
ridges or denticulations along their sides, those being limited to the outer margin of the 
joint-face. They are usually therefore of greater size than the corresponding parts on 
the stem-joints of Hxtracrinus and Pentacrinus, which are sometimes much constricted 
by the development of ridges at their sides. The stem-joints of Balanocrinus, therefore, 
are somewhat like those of Millericrinus; though in the latter type the whole joint- 
face is uniform in character, and not marked out into sectors as is the case in the Penta- 
erinide. Many Paleocrinoids have jomts somewhat like those of Balanocrinus, ‘.e., 
crenulated round the edge, but nothing more. The genus commenced with Pentacrinus 
in the Trias, and survived to the Lower Neocomian, no remains of it having yet been found 
at any higher horizon ; while I have not met with this simple form of stem-joint in any 
recent species. 
Owing to the deficiency of our knowledge respecting the nature of the calyx of 
Balanocrinus, I have found it necessary to use the characters of the stem as the basis of 
the classification of the family. Balanocrinus may have under-basals like Haxtracrinus, 
or more than three radials like Metacrinus; but until we know more about its calyx a 
classification of the Pentacrinide must depend primarily upon the varying features of the 
stem. 
I. Five to eight large teeth at the sides of each petaloid sector, most of which start from the outer edge 
of the joint-face, while the remainder meet their fellows in the interpalmar spaces. 
1. Three radials, . : : : : : c : . Pentacrinus, 
2. More than three radials, . : : . Metacrinus. 
IL. Sectors linear with delicately crenulated ages! Under- basals. The first eter much prolonged 
downwards. Secondary arm-trunks each bear a succession of armlets on the same side, Lzxtracrinus. 
III. Joint-faces crenulated round the edge only, not along the sides of the sectors, . Balanocrinus. 
Three other supposed genera have also been referred to this family. One is [socrinus, 
von Meyer,’ of which the stem is scarcely known ; while it is probable that von Meyer’s 
description of the primary rays as consisting of but two joints, basals being likewise 
wanting, is also somewhat incorrect. The mode of division of the rays, on which von 
Meyer laid considerable stress, is perfectly normal. I prefer therefore to refer the type, 
temporarily at any rate, to the genus Pentacrinus, as has been done by Bronn and 
others, though I will not attempt to follow them into specific details. 
Another unrecognised genus of the Pentacrinide is the Chladocrinus of L. Agassiz.’ 
After defining the stem of Pentacrinus as “ portant de distance en distance des rayons 
simples verticillés,” he continued, “on pourra désigner sous le nom de Chladocrinus les 
especes dont les rayons accessoires forment des verticillés plus ou moins distans.” 
1 Tsocrinus und Chelocrinus, Museum Senckenbergianum, Frankfurt, 1837, p. 251. 
* Prodrome d’une Monographie des Radiaires ou Echinodermes, Mém. de la Soc. des Sci. Nat. de Neuchatel, t. i., 
1835, p. 194. 
