IN THE DEVELOPMENT OF COMATULA. 



251 



have the sides of the roof taking the place of inter-radialia, — in other words, 

 having the exact value of the parts which so closely resemble them in the larval 

 Comatula, while the radialia are either not developed at all, or are so minute as 

 to have escaped notice in the fossil (woodcut, fig. 6). According to this interpre- 

 tation the formula of the composition of Lageniocrinus would stand as follows : — 



Basalia, .... 



3 



(two large and one small.) 



Parabasalia, 



5 





Radialia, .... 







(or inconspicuous.) 



Inter-radialia, . 



o 





Arms, .... 









Until we know more of the structure of this very rare little fossil, we shall be 

 at liberty to adopt either of the above inter- 

 pretations ; but it may be remarked that the ^'^- ^• 

 view taken of the composition of the calyx of 

 Lageniocrinus in the second of these interpre- 

 tations is exactly that which we must take of '' ^ 

 the calyx of the larval Comatula, viewed apart v ^ 7 

 from the roof, if, with certain authors, we con- x^^ '^ j\ \ ^ ' /\\ 

 sider the centro-dorsal piece in Comatula as \. // '^ yTCjf^ *"' \\ 

 representing a zone of united basalia (see page '^^^'wx^T"^ 

 245) ; for then the basalia, in my analysis of <C -/ ; \ > 

 the larva given above, will become parabasalia, 

 a view, however, which, from reasons already 

 stated, I am not disposed to adopt, and which 

 is not necessary for the comparison here in- pto/io/ Lageniocrinus. 



Sisted on. l- Basalia 3 



_-, ii'ir«ir-f r !'• Parabasalia, o 



Between our pre-brachial fixed Comatula 3. intei-radiaiia 5 



and the Blastoidea, with their high pyramidal 



five-sided roof, there is, on a superficial view, so strong a resemblance, that 

 we are at first tempted to consider them as both constructed on the same 

 plan. They have, however, really very little in common ; for although the inter- 

 radialia take part, sometimes largely {Elwacrinus) in the formation of the roof, 

 yet the so-called pseud-amhulacra^ with their singular and complicated structure,* 

 and the system of ovarian apertures, seem to place the Blastoidea in a group so 

 widely distant from Comatula as to afford but few points of real agreement with 

 our larva. 



With Cwpressocrinus also, so very remarkable by its tall pyramidal shape, 

 the resemblance is only apparent, the sides of the roof- pyramid in Cupressocrinus 

 belonging without doubt to the radial, and not to the inter-;radial system of the 

 Crinoid. 



* See RoMER, Monographie der Blastoideen. Arcliiv. f. Naturg. 18.50. 



