REPORT ON THE CRINOIDEA. 65 



which represents a recent generic type first discovered by Semper and named by him 

 Ophiocrinus. In consequence, however, of the preoccupation of this name it has been 

 since changed to Eudiocrinus. Thus then the great number of generic names which 

 have been given to the fossil Comatulse become reduced to three, Antedon, Actinometra, 

 and Eudiocrinus. Three new genera have been established by myself for new types of 

 recent Comatuke, viz., Atelecrinus, Promachocrinus, and Thaumatocrinus ; and these 

 six are all that could strictly be included in the family Comatulidas until quite recently. 

 Pictet 1 has also referred to it both Marsupites and Saccocoma, but Dujardin and 

 Hupe 2 removed Marsupites to the Cyathocrinidae, and added to the Comatulidae 

 the sessile Eugeniacrinus and its allies, which had been grouped under the Eugenia- 

 crinidae in Bronn's " Thierreich." Zittel a restored this family to its proper position 

 and restricted d'Orbigny's name to the Feather-stars proper; while Saccocoma was 

 replaced in Midler's group, the Costata, which had been established for- its: reception 

 in 1840. 



Quite recently, however, it has become necessary to add a seventh genus to the 

 family, viz., the fossil Thiolliericrinus, which represents a permanent form of a late 

 stage in the development of the Antedon-laYva. It has been well described by 

 de Loriol 4 as an Antedon with a Bourgueticmius-stera. The stem-joints of the 

 larval Antedon are closely similar to those which are characteristic of the family 

 Bourgueticrinidae, their faces bearing strong transverse ridges with a deep fossa on 

 each side. 



In ordinary Comatulae the centro-dorsal, after separating from the stem beneath it, 

 soon loses all trace of its previous connections, owing to a more or less extensive deposi- 

 tion of limestone at its dorsal pole ; whereas in Thiolliericrinus the connection between 

 the lower stem-joints and the cirrus-bearing centro-dorsal seems to have been maintained 

 much longer, if not throughout life. For the under surface of the centro-dorsal bears a 

 well-developed articular facet like that on an ordinary stem-joint of Bourgueticrinus or 

 Rhizocrinus. It would appear therefore that the centro-dorsal with the few cirri which 

 were developed upon it remained permanently attached to the stem below, so that 

 Thiolliericrinus would represent the permanent condition of an Antedon-larva during the 

 development of its second whorl of cirri. We cannot be absolutely certain about its 

 characters, however, until an entire example of the genus has been discovered. But 

 the presence of an articular facet on the under surface of its centro-dorsal is a feature 

 which is sufficient to distinguish it very markedly from the six genera of recent 

 Comatulae. 



1 Traite de Paleontologie, Paris, 1857, vol. iv. p. 287. 



2 Op. cit., p. 186. 



3 Handbueh der Palaeontologie, Bd. i., Abth. 1, p. 395. 



4 Description de quatre Echinodermes Nouveaux, Mem. Soc. Pal. Suisse, 1880, vol. vii. p. 10. 



(ZOOL. CHALL. EXP. — PART LX. — 1887.) 000 



