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



he says, " Auf deniletzten Saiilengliede ruhen fiinf Beckeuglietler, und auf jedem derselben 

 em Bippen- ( = second radial) undein Scliulterglied (third or axillary radial), auf welchem 

 zwei einfache Arme eingelenkt sind," from which it is evident that he was wrongly led 

 to regard the first radials as representing the basals of Comaster and JPentacrinus. This 

 mistake is hardly a surprising one when we consider the remarkable metamorphosis 

 undergone by the embryonic or primitive basals, and their concealed condition in the 

 adult Coinatula mediterrcmea. 



Midler, who examined a very large number of species of Comatula, never found one in 

 which the basals appeared externally, as described and figured by Goldfuss in Comaster, 

 and remarked ' : — " Daraus geht hervor, dass die Gegenwart wirklicher Basalia ohne Zer- 

 legung bei einer lebenden Comatule, auch dann, wenn sic wirklich solche besitzt, schwer 

 zu erkennen sein muss. Die Unterscheidung der Comaster uud Comatula wird daher 

 bei der Ordnung der lebenden Comatulen unpractisch." In fact he appears to have 

 given up the genus Comaster altogether ; for he adds in a note : — " Kurzlich habe ich 

 die einzige im Museum zu Bonn befindliche Comatula mmltiradiata (nicht das von Goldfuss 

 zerlegto Exemplar, wovon ich nichts mehr vorfand) untersucht. Ich habe daran nichts 

 von Beckenstiicken erkennen konnen. Die Gattung Comaster ist daher wohl zu un- 

 terdriicken." He seems finally 2 to have thought that it might possibly be identical 

 with the C. Bennett I of the Ley den Museum. As, however, Comaster has not been seen 

 by any naturalist since the time of Goldfuss, its position must still remain in doubt. 



(§8) Up to the time of Midler no one paid any attention, from a systematic point of 

 view, to the arrangement of the tentacular furrows on the ventral perisome of the disk of 

 Comatula ; but Lamarck and De Blainville had, as we have already seen, examined and 

 described, with more or less accuracy, a condition which we now know to differ very 

 considerably from that presented by the Decacnemus of Linck, or the Antedon of De 

 Freminville. Both these observers seem to have regarded the former condition as the 

 normal one, and as common to all Comatuhe. Midler, who does not seem to have been 

 acquainted with their descriptions (for he makes no mention of them), took up the subject 

 systematically, and soon discovered that, using the distribution of the tentacular furrows 

 as a basis of classification, he could distinguish two, as he thought, very distinct types 

 of the genus Comatula, which he named Alecto and Actinometra respectively. In his 

 earlier communications 3 on the subject he described the ordinary Comatula and Penta- 

 crinus as having a central mouth and symmetrically distributed tentacular furrows; 

 i. e. the five main trunks formed by the union of the furrows of the five groups of arms 

 converge directly towards the centre of the disk, being separated by five "interpalmar " 

 areas, one of which, slightly larger tban the rest, is occupied by the anal tube, which is 

 therefore excentric in its position (PI. I. fig. 5, An.). 



During his visit to Vienna in 1810 Midler had an opportunity of examining an un- 



1 'Uebcrdie Gattung Comatula, Lam., und ihre Arten,' Separatabdruck aus den Abhandl. Berlin. Akad. lS49,p. 8. 



a Ibid. p. 29. 



3 " Ban des Pentacrinus" loe. cit. p. 47, and Wiegm. Arcbiv, 1S40, i. p. 311. 



