Reviews, — Wachwiuth 8^ Springer's Monograph on Crinoids. 325 



Herpetocrinus they afford the only means by which species can be 

 distinguished. 



It is a remarkable fact that some genera and species which appear 

 closely allied differ in the mode of growth of the stem. " The 

 internodes of some species begin at quite a distance from the calyx, 

 while others have no internodal joints at all." In the Ichthyocrinid^ 

 the proximal region of the stem consists of low ossicles, with no 

 internodals, varying from 20 to 50 but nearly constant in number in 

 the same species. Flatycrinus has no internodes, but Marsupiocrinus 

 has them well defined. Mespilocrinus has no internodals. Bliodocrinus 

 has " but a single ossicle to each internode." Two Gotland species 

 of Gissocrirms (6r. typus and G. campanula) are much alike, and 

 often I was only able to distinguish specimens by the number of the 

 internodals, a feature imperceptible to the unaided eye. 



Further study of the mode of growth, of external ornament, of 

 joint surfaces, of the shape of the axial canal, and of the relations of 

 cirri, with the consistent tabulation of these characters, may some 

 day enable us to draw up a key. The difficulties are two : the 

 changes of character in the different regions of the same stem ; and 

 the extreme rarity of complete stems in association with crowns. 

 Still the work has to be done, and the amount already accomplished 

 by Messrs. Wachsmuth and Springer suggests that the task is no 

 impossible one. Let the student enter the field to which they have 

 pointed the way. 



Further remarks on minor points suggest themselves. 



" In a few Palgeozoic Crinoids, the whole stem is divided longi- 

 tudinally, its joints being either quinque- or tri-partite. The former 

 is the case in Ohiocrinus, Ectenocrinus, Barycrinus, Anomalocrinus, 

 and probably others ; while a tripartite stem has been observed only 

 in Heterocrinus" (p. 41). In this sentence the names Ectenocrinus 

 and Heterocrinus should be interchanged. The words " probably 

 others " understate the case, since a quinquepartite stem has already 

 been described and figured for Cleiocrinus,'^ Thenar ocrinus,'^ Botryo- 

 crinus,'^ Mastigocrinus,'^ Streptocrinusj^ Ottaioacrinus,^ Euspirocrinus,- ^ 

 Vasocrinus dilatatus, Calceocrinus pinnulatus, ^ and Bliodocrinus 

 asperatus,^ while traces of similar sutures have been proved in 

 Herpetocrinus.'^ Other examples of quinquepartite stems are known, 

 but have not yet been referred to any genus. In short a large 

 number, if not the majority, of Lower Palasozoio genera had the 

 stem so divided. The character is obviously a primitive one, but its 

 meaning need not again be discussed.'' 



Another sentence, suggesting that this section was written many 

 years ago and has escaped revision, is the statement that " In the 

 Cyathocrinidae the structure at the lower part of the stem is only 

 known in Barycrinus." I should not put Barycrinus in the Cyatho- 

 crinidse myself; but if it is to go there, so also must Botryocrinus, 

 Ifastigocrinus (which, indeed, Wachsmuth considered " merely 



1 By E. Billings. "- By F. A. Bather. ^ By W. E. Billings. 



* See " Eoyal iNfatural History," vol. vi, pp. 296-7 ; Warne & Co., 1896. 



