44 p. H. CAllPENTJGE ON C0MATULJ3 EKOM 



which were known at that time were the various species of Solano- 

 crinus*, the so-called Comasterf of Lundgren, and the three small 

 centrodorsal pieces described by Edward Forbes 4: from the Coralline 

 Crag. These last, having no calyx attached, proved nothing either 

 way. The same was the case with the isolated centrodorsal piece of 

 Glenotremites, the interradial grooves on which were described as 

 "ambulacra" by Goldfuss, and as sockets for the attachment of the 

 arms by Agassiz, Eomer, Pictet, and Geinitz. Their real nature as 

 surfaces of attachment for the basals was first made clear by Lund- 

 gren §. The so-caUed Comaster, discovered by Schliiter, and first 

 described by Lundgren, has a centrodorsal with all the characters of 

 Glenotremites, viz. a more or less distinct dorsal star, and on the 

 ventral surface radial pits separated by interradial grooves. One 

 specimen retaining the calyx attached to the centrodorsal piece 

 resembles Solcmocrinus in the presence, above the interradial angles 

 of the centrodorsal, of external basals which obviously occupy the in- 

 terradial grooves on its ventral surface. Here, then, is the real ex- 

 planation of the " ambulacra " of Glenotremites ; and Schliiter was 

 naturally entitled to suppose that all the Comatidce described by him 

 with these interradial grooves had corresponding external basals 

 like those of Comaster {Antedon) Betzii, and presumably, therefore, 

 no rosette. 



It is noteworthy, however, that in A. lenticularis and A. italica, 

 two out of the three species with the calyx preserved, Schliiter had 

 some difficulty in detecting the presence of external basals. In the case 

 of A. lenticularis he can only describe them as apparently showing 

 themselves in two places, beneath the sutures of the united first ra- 

 dials ; while he neither describes nor figures them in A. italica, though, 

 since he says they are present in all the fossil species examined by 

 him, it is to be supposed that they exist in this one. An analogous 

 case to that of Schliiter's specimen of A. lenticularis, viz. basals 

 appearing externally at some of the angles of the calyx, but not at 

 others, will be noticed further on in A. cequimarginata (PI. V. 



fig- 4)- 



The variations are perfectly explained by what is now known 



respecting recent Comatulce. I pointed out in 1877 1| that in some 



species of Actinometra the rosette is connected with five prismatic 



or cylindrical rods that lie in a stellate series of interradial grooves 



(the basal grooves) on the ventral surface of the centrodorsal piece. 



" These five rods, to which, taken together, the author has given the 



name of the basal star, vary very greatly in the degree of their 



development, not only in diflPerent species, but in difierent individuals 



* Goldfuss, it is true, says nothing about such grooves, but merely speaks 

 of tbe basals as articulated on "fiinf strahlenformige Erhabenheiten." These 

 interradial elevations were, however, grooved as in recent Comatulcs. Quenstedt 

 (' Echinodermen,' p. 173) describes them as ** gefurchte Strahlen." 



t " Om en Comaster och en Aptyclius fran Kopinge," Ofversigt af Kongl. 

 Vetenskaps Akademiens Forhandlingar, Stockholm, 1874, No. 3, p. 69. 



\ " Echinod&rmata of the British Tertiary Deposits," Palaeontogr. Soc. 1852, 

 pp. 19, 20. 



§ Oi^. cit. p. 65. 11 Journ. Linn. Soc. he. cit. p. 452. 



