328 Reviews — Wachsmuth 8f Springer's Monograph on Crinoids. 



common in various Paleozoic genera. In Actinocrinidge, Platy- 

 crinidge, and other forms " the terminal part tapers rapidly to a 

 point, and cirri are given oif from the sides." This end is " not 

 homologous with the part by which the young Crinoid had been 

 formerly attached, but is a product of later growth." But all this 

 has nothing to do with the character of the original distal end. 

 The term dorso-central was applied to the distal segment of the 

 stem in the larval Antedon rosacea (or A. bifida) because it was seen 

 to be a flat cribriform plate, whereas the penultimate segment was 

 an elongate columnal formed of fasciculate stereom. The necessity 

 for a distinct term depends on two considerations : (i) the 

 nniversalit}^ of the occurrence of such a plate ; (ii) the morphological 

 difference between cribriform and fasciculate stereom. As to (i), 

 Wachsmuth and Springer infer from the development of Antedon and 

 from palseontological evidence, " that the young PalaBocrinoid in its 

 early life was attached by a dorso-central." But the palaeontological 

 evidence adduced is of the slenderest description: "In only two 

 instances do we know that [adult] Palaeozoic crinoids were attached 

 by what appears to have been originally a dorso-central plate : 

 in ' Cheirocrinus' clarus^ and in Eucalyptocrinus crassus."'^ The 

 foi'mer instance shows an encrusting root with lobate edges ; the 

 latter shows a slight terminal swelling fi-om which proceed numerous 

 branching, radical cirri. Our authors consider the lobations of 

 the former as ' budding cirri,' while, with reference to the well- 

 known roots of Eucalyptocrinus, they write : " These roots seem to 

 have been derived from a central disk (dorso-central), from which 

 the numerous branches were given off in a similar manner as the 

 immature cirri from the terminal plate of ' Cheirocrinus ' clarus." 

 The only other instance of a terminal plate quoted by them is from 

 the Hudson River group of Cincinnati. Here " we occasionally find 

 crinoidal disks, attached to pieces of coral, which closely resemble 

 the dorso-central of Antedon. These disks have a pit or depression 

 at the middle of the upper face, sometimes enclosing a small stem 

 joint. They are irregularly round, and some of them have small 

 j)rocesses passing outward from the sides, which seem to represent 

 primitive cirri." Clearly these objects are of the same nature 

 as those from the Niagara group of New York, to which Hall gave 

 the name Aspidocrinus. It is conceivable that they are, or may be, 

 of the same nature as the terminal plate of Antedon rosacea. But 

 these three or four instances are scarcely evidence that all or even 

 the majority of Palaeozoic crinoids were at one time of their lives 

 attached hj a dorso-central. An encrusting root is not necessarily 

 the homologue of a single cribriform plate, as study of the root of 

 Apiocrinus will speedily reveal to anyone. Besides, admitting 

 the secondary nature of many branching or tapering roots, we have 

 no evidence that they were preceded by dorso-centrals. But, 

 turning to (ii), we ask whether there really is any difference 



" 1 N.Y. State Cab. Nat. Hist. ; Fifteenth Eep., PI. i. Figs. 17 and 18." 

 " 2 N.Y. State Mus. Nat. Hist. ; Twenty-eighth Eep., PI. xvii, Fig. 5." 



