268 THE VOYAGE OF H.M.S. CHALLENGER. 



tentaculiferous. Neither arms nor pinnules have any distinct ambulacra! skeleton, and 

 sacculi are altogether absent. Some of the lower pinnules have terminal combs. 



History. — This generic name was proposed by Midler 1 in 1841 for a fine specimen of 

 Comattda Solaris, Lamarck, which he had examined at Vienna in the previous year. He 

 had not then seen the type of Lamarck's species, and seems to have assumed that it was 

 an eudocyclic form like Pentacrinus and the three European Comatulae, i.e., that the disk 

 bore five ambulacral grooves converging upon a central mouth. 



This is not the case, however, in reality, for Muller discovered on a later visit to Paris 2 

 that the disk has the same peculiarity in Lamarck's types of Comatula Solaris, as in the 

 large Vienna specimen " welche generisch von andern durch die Bildung ihres Scheitels 

 verschieden zu sein schien. Auf dem Scheitel der mit blumenartigen Kalkblattchen 

 bedeckt ist, ist keine Spur von den Furchen zu sehen die bei den Comatulen von den 

 Armen zum Munde fiihren. Auch ist dort nichts vom Munde zu sehen. Die mitte der 

 Bauchseite nimmt eine Bohre ein. Die Arme haben die ventrale Furche der Comatnlen, 

 die Furchen der 10 Arme mtinden aber in gleichen Abstanden in eine die Seheibe am 

 Bande umziehende Cirkelfurche. Diese eigenthiimliche Bildung liesse sich durch eine 

 unsymmetrische Vergrosserung desjenigenlntertentacularfeldes worin die Afterrorhe steht 

 liber den ganzen Scheitel, und auf Kosten der anderen Intertentacularfelder erklaren, so 

 dass der Mund aus der Mitte des Scheitels ganz an die Seite zwischen je 2 Armen 

 gerath." Owing to the dry state of the Vienna specimen the exact position of the mouth 

 could not be determined ; and the same difficulty presented itself with the types of 

 Asterias multiradiata and Asterias pectinata, Betzius, which Muller examined in the 

 Betzian collection at Lund, and found to present "ganz dieselbe Bildung des Scheitels" as 

 the Vienna specimen. 3 



In the absence of better-preserved material Muller hesitated to make a definite generic 

 separation of these three Comatulae from the ordinary endocyclic species. But in 1844 

 he visited the Paris Museum and there found several Comatulae in spirit with the same 

 arrangement of ambulacra on the disk as he had described in Actinometra imperialis and 

 in the two Betzian species, i.e., a circular furrow extending round the greater part of the 

 margin of the disk, with the ambulacra of the primary arms opening into it at tolerably 

 regular intervals, very much as in PI. LVII. fig. 3. The number of ambulacra converging 

 on the excentric mouth would thus be less than five, and in fact was reduced to three in 

 two of the three individuals first seen by Muller. This character, and not the position 

 of the mouth, was regarded by him as the most distinctive peculiarity of Actinometra. 

 For he found that some species may have a central anal tube and excentric mouth " ohne 

 dass die Ambulacra ihre symmetrische Vertheilung auf die 5 Armstamme einbiissen." 4 



1 Monatsber. d. k preuss Akad. d. Wiss. Berlin, 1841, p. 180. 2 Ibid., 1846, p. 178. 



3 Archivf. Naturgesch., 1843, Jahrg. ix. Bd. i. pp. 132, 133. 



4 Monatsber. d. k preuss. Ahul. d. Wiss. Berlin, 1846, p. 177. 



