MONOGBAPH OF THE EXISTING CRINOIDS. 581 



may be supplemented by the appearance of additional radicular cirri on the long 

 axes of some of the immediately preceding columnals and of sporadic attachments 

 elsewhere. 



In the different species the development of the terminal stem plate may cease 

 anywhere between the extremes mentioned; but it always follows the same course 

 in every individual, no matter what the species. 



The terminal stem plate is absent in Thaumatometra nutrix, in which species 

 the distalmost columnal attaches itself to an expansion of the distal end of a 

 pinnular. 



The terminal stem plate is circular or slightly lobate in 



C 'omac.tinia. meridionalix. Antedon petasus. 



Comissia littoralis. Antedon bifida. 



Ptilometra mulleri. Antedon mediterranea. 



Crotalometra porrecta. Antedon adrlatwa. 



[fGlyptomctra tuberosa"]. Compsometra loveni. 



Leptometra celtica. 



It is deeply stellate with five long tapering extensions in Promachocrinus 

 kerguelensis. 



It is strongly digitiform in Hathrometra prolixa and Hathrometra tenella. 



It is strongly and irregularly digitiform, more or less completely transformed 

 into radicular cirri, and supplemented by true radicular cirri and extra attachments 

 in Heliometra glacialis and Hathrometra sarsii. 



From this it would appear that the development of the terminal stem plate 

 is correlated with the length and slenderness of the column. 



Attachment. The larvae of the comatulids show great diversity in their choice 

 of objects to which to attach themselves. They fall in this respect into two main 

 groups (1) those which will attach themselves to almost anything, and (2) those 

 which will attach themselves only to large individuals of the same species. These 

 latter again fall into two groups (a) those which will attach themselves only to 

 the cirri, and (6) those which will attach themselves only to the pinnules. 



The pentacrinoids of the following species are found attached to various 

 objects : 



Tropiometra macrodiscus. Compsometra serrata. 



Tropiometra picta. Compsometra loveni. 



Crotalometra porrecta. Leptometra celtica. 



Glyptometra tuberosa. *Heliometra glacialis. 



Antedon petasus. Promachocrinus kerguelensis. 



Antedon bifida. Anthometra adriani. 



Antedon moroccana. Florometra serratissima. 



Antedon mediterranea. *Hathrometra prolixa. 



Antedon adriatica. Hathrometra tenella. 



Hathrometra sarsii. 



The two species marked with an asterisk (*) are also found attached to the 

 cirri of larger individuals. 



