438 



MERISTIC VARIATION. 



[part I. 



III.), de Loriol, P., Me'm. Soc.paUont. Suisse, 1877—1879, p. 245, 

 PL xix. figs. 39 b, 40 a, 41 a. 



I 



m 



Fig. 131. I. Normal four-rayed basal of Tetracrinns moniliformis (from Birmens- 

 dorf). II. A three-rayed basal of the same species from the same locality as I. 

 III. A five-rayed basal of the same species from Oberbuchsitten. 



(After P. de Loriol.) 



f 667. Cupressocrinus gracilis. This form has normally a 5-rayed 

 calyx, and a 5-sided basal plate containing only 4 canals round 

 the central canal (Fig. 132, I.). Varieties have been seen in which 



667 a. 



668, 



Fig. 132. Cupressocrinus gracilis. The normal form of the basal is shewn in 

 I. A form with five canals round the central is represented in II, and in the 

 specimen shewn in III there are three peripheral canals. See No. 667 a. 



(After L. Schultze.) 



there are 5 (Fig. 132, II.), or 3 (Fig. 132, III.) such peripheral 

 canals. The stalk is normally 4-sided, but in the varieties it is 

 either 3- or 5-sided in correspondence with the number of canals. 

 C. elongatus : stalk may be either 4- or 5 -sided. The 

 species C. injiatus has normally 3 canals in the (circular) stalk. 

 Schultze, L., Denkschr. At Wiss., Math.-nat. CI., 1867, xxvi. 

 pp. 130 and 136, PI. I. fig. 2 b, and PI. III. figs. 2 c and 2 i. [Cp. 

 No. 667.] 



Abnormalities in the manner and frequency of branching in the arms of Crinoids 

 leading to great numerical variation have been often recorded. See Carpenteb, 

 Chall. Hep., xxvi. Pt. lx. p. 28; id. Phil. Trans., 1866, Pt. 2, p. 725 PL, also a case 

 of twelve arms in Antedon rosacea, the abnormality not being symmetrical, Dendy, 

 Proc. R. Phys. Soc. Edin. , ix. p. 180, PI. ; also case of A. rosacea having abnormal 

 branches in two arms symmetrically placed with regard to the axis. Bateson, W., 

 P. Z. S., 1890, p. 584, fig. 4 (now in Coll. Surg. Mus.). The abnormal arms were 

 b. 2 and e x of the usual nomenclature, as shewn in Fig. 133. For details see original 

 description. 



*6G9. Encrinus liliiformis : amongst other abnormalities case 

 given in which one of the radii bore only one arm. v. Strom- 

 beck, Pakeont, iv. p. 169, PI. xxxi. fig. 3. 



