ME. P. H. CAEPENTEE ON THE GENUS ACTINOMETEA. 7 



in preference to it, paid very little attention to the soft parts of either of the Comatula? 

 which he dissected. 



In the following 1 year, however, De Blainville ' described the visceral mass at some 

 length. Like his predecessors, he adopted Lamarck's genus Comatula, making it the 

 only representative of his section, " Les Asterencrinides libres," while at the same time 

 he acknowledged the prior claims of de Ereminville's name Antedon. He was, of course, 

 acquainted with Lamarck's error respecting the position of the mouth, which he 

 described as " assez anterieure, isolee, membraneuse, au fond d'une etoile formee par cinq 

 sillons bil'urquc's." The species which lie dissected was a foreign one preserved in 

 spirit ; it had a large number of arms ; and from the not very clear description which he 

 gives of its ventral surface it would seem to have been a true Actinometra. 



After speaking of the tentacular furrows on the ventral surface of the arms, he says 2 , 

 " En suivant ces especes de sillons dont lc nombre est proportionnel a celui des digitations 

 du rayon, on arrive par un sillon unique pour chacun d'eux et qui en occupe la base, au 

 centre d'une sorte d'etoile a bords epais, franges, et par suite a la bouche qui est au fond. 

 L'etoile formee par la reunion des sillons des rayons n'est pas symetrique, c'est a, dire que 

 ses branches sont tres-inegales : les unes que j'appellerai les anterieures, etant bien plus 

 courtes que les autres, ou posterieures. II en est resulte que la bouche n'est pas au 

 centre de l'etoile, mais bien plus proched'un cote quede 1' autre : elle est assez difficile a. 

 voir au contraire d'un autre orifice, dont il va etre question, et que M. de Lamarck 

 paroit avoir pris pour elle. Elle est profondement enfoncee dans l'etoile des sillons : elle 

 est ronde, sans aucune armature et conduit immediatement dans l'estomac." 



The above description implies, if I rightly understand it, that the mouth of De Blain- 

 ville's specimen was nearer to one side of the disk than to the other, so that the primary 

 trunks of the ambulacral grooves were of unequal lengths. This will be subsequently 

 seen (section 14) to be the principal distinctive character of the genus Actinometra. 



De Blainville evidently attached no importance to the position of the mouth as a 

 character of systematic value in the determination of the species of recent Comatulce ; 

 and from his definition of it as " assez anterieure," it would almost appear as if he 

 supposed the other species to agree in this respect with the one dissected by him. 



This is, in fact, the case in five out of the eight species described by Lamarck, with 

 which De Blainville was probably acquainted, and to which he added no new ones, 

 except that he gave the name of Comatula barbata to Linck's third species of Decaciiemus, 

 the fimbriata of Barrelier, or " barbata " of Linck. Lamarck had been uncertain to which 

 of his species he should refer it, although, as we have seen above (section 1), it is really 

 only a local variety of his C. medilerranea. 



Like the other naturalists of his time (1S38), Agassiz 3 also adopted Comatula in preference 

 to the other generic names of this type, but defined it as having the " bouche centrale en- 

 foncee," and with the five " rayons du disque bifurques," thus limiting the number of 

 arms in the genus Comatula to ten only. At the same time he erected Lamarck's species 

 C. multiradiata, with sixty or more arms, into a new genus, Comaster, which he defined as 



Manuel d'Aotinologie, (Paris, 1834) p. 2 19. : Op. cit, p. 251. 



" Prodrome d'une Monographic des Eadiaires ou Echinodernies," Ann. des Scicu. Nat. 2 e serie, Zool. vii. p. -~>7. 



