ME. P. H. CARPENTER ON THE GENUS ACTINOMETRA. 13 



Lund specimen as belonging to the type of his new genus Actinometra, in which not five, 

 as in Alecto, hut " weniger Furchenstamme den excentrischen Mund erreichen." 



Midler further examined a specimen of the " so-called " C. multiradiata in the Bonn 

 Museum ; and although he did not actually include it in his type under that name, yet 

 he seems to have been inclined to do so ; for he says 1 that " es stimmt durch den Besitz 

 der Syzygien an den Axillaria der Anne mit Comatula multiradiata Betz., " hut adds, 

 " Maul excentrisch, 5 Burchen der Scheibe sammeln die Burchen der respectiven 

 Arme und kommenam Mund zusammen." (See Bl. I. fig. 4.) Here, again, it is evident 

 that Midler's description of Alecto will not hold good ; for according to his own descrip- 

 tions, the Lund and Bonn specimens of Comatula multiradiata, Mull., however much 

 alike in other respects, differ so greatly in the distribution of the ambulacra on the disk 

 that one is Actinometra and the other Alecto. 



Miiller also referred three specimens contained in'the Baris collection to this type ; and 

 he was perhaps thinking of the condition of the ambulacra presented by them when he 

 added the following sentence to his previous description of the Lund specimen, and 

 named the type Alecto 2 . " Mund excentrisch, aber an Weingeistexemplaren ergibt sich 

 dass die fiinf zum Munde fiibrenden Burchen sich ganz symmetrisch fur die fiinf Gruppen 

 der Arme vertheilen." This arrangement, which he called the "gewohnliche Anordnung 

 der Burchen," had been already 3 figured by him as occurring in C. 'multiradiata, which, 

 as he says, differs from the ordinary C. mediterranea in the excentric position of the 

 mouth (PL I. figs. 1, 1). 



It is thus evident that, according to Midler's own nomenclature, two types, differing 

 only in the "Bilduug des Scheitels," but almost precisely similar in every other respect, 

 viz. the Lund specimen, on the one hand, and the Baris specimens, on the other, were 

 referred by him to the same species, Alecto multiradiata, Miiller. It will, however, 

 be shown further on that the distinction drawn by Miiller between Alecto and Actino- 

 metra is not a real one, and that the Lund and one of the Baris specimens, both of which 

 have an excentric mouth and a central or subcentral anal tube, really belong to one and 

 the same species, Actinometra multiradiata. 



(§ 10) Bor a short time after the publication of Midler's Comatula-memoirs the genera 

 Alecto and Actinometra remained as he left them, both being regarded as subordinate 

 types of Lamarck's genus Comatula. 



A singularly minute fossil species, discovered by Bhilippi 4 between the valves of an 

 Isocardia cor from the Sicilian Tertiaries, was named by him Alecto alticeps because of 

 the height of its " Kelchstiick," a character found both in Alecto Eschrichtii and in 

 A. phalangium, as Midler had already pointed out. A few new fossil species of a more 

 or less doubtful nature have been since described, and variously referred cither to Mid- 

 ler's family Comatulinae or to new and distinct types. 



The typical genus of this family, Comatula, Lam., has undergone numerous changes in 

 its definition. Bcemer, who at first revived Linck's name Decacuemus, subsequently 



1 'Gattung Comatula,' p. 29. : Ibid. p. 26. 3 Ibid. p. 9. 



4 " Alecto alticeps, n. sp., eine tertiiire Comatula-Art von Palermo," Neues Jahrb. fur Mineral. 1S44, p. 540. 



