80 Br. C. F. Liitken — On the Ophiuridw. 



characterize d chiefly by " un disqiie a peine distinct ;" but this fossil 

 is evidently a true species of Ophiocoma, having lost its disc, a very 

 common accident with OpJiiurid(B, especially w^hen the disc is more 

 or less soft. D'Orbigny's Ophiurella bisjnnosa is only known from a 

 short diagnosis, and should be more fully described. Ophiura 

 GriesbacJiii. Wright (with a very distinct disc), has nothing in 

 common with the typical species of the genus ; its true position I 

 cannot decide, it has the general aspect of an Ophioglypha, Lyman, 

 (^Opliiura, Forbes). The genus Opliiurella must of course be elimi- 

 nated from the catalogue. The genus Acrura is based upon the A. 

 prisca. Miinst., of the Trias, a species that appears to be closely 

 related to AmpJiiura, Forbes ; and if it be retained as the type of a 

 peculiar genus, it cannot be clearly defined. The best preserved 

 fossil, Ophiuridce, almost always want those organs of the superficial 

 tegumentary system,— teeth, papillae of the mouth and arms, spines, 

 spinules, granulations, etc., — which are so important for the deter- 

 mination of the recent species ; they can therefore be referred but 

 exceptionally to their true genera. Nor, if they belong to extinct 

 types, can they be properly characterized, owing to their imperfect 

 preservation. In some instances also the true arm-plates are more 

 or less completely lost, and then all that can be said, is, that the 

 fossil is a typical Ophiuroid, but of its affinities hardly a guess can 

 be made ; cases will be cited further on. Acrura Cottaldina and 

 A. snhnuda, D'Orb., are only known from insufficient diagnoses, and 

 are therefore at present indeterminable. A. Cornuelana, and A. 

 serrata, Eoem., are probably best placed in the recent genus- Ophio- 

 glypha, Lym. 



Acrura Brodiei, Wr. is one of those very imperfectly known forms 

 that might well be placed provisionally in the old genus Ophiura, 

 Possibly Aspidura loricata, Goldf. is really the type of a peculiar 

 genus, but I do not know how to characterize it satisfactorily. The 

 characters given to all these genera by D'Orbigny are really value- 

 less, and are based on no knowledge whatever of the characters of 

 the recent Brittle-Stars. Count Mtinster's figure of the same form 

 is also incorrect ; the star of small scales, filling up the aperture of 

 the mouth, does not exist in nature ; the animal had the tj'^pical 

 mouth of an ordinary Ophiuroid. If Hagenow's figure of Aspidura 

 Ludeni (copied by D'Orbigny and Vogt as that of Palmocoma Fur- 

 stenhergii ! } be compared with the preceding species, a certain 

 general resemblance of aspect will be found, but no evidence of 

 generic identity. Picard's Aspidura squamosa, and A. coronceformis 

 would have been better placed with Amphiura or with Acrura. 

 Aplocoma {Haplocoma ? ) Agassizii is quite indeterminable. I do not 

 deny that Geocoma carinata and lihanotica have some characters 

 apparently in common : they somewhat recall badly preserved speci- 

 mens of OphioiJirix, but I do not see any likeness between them and 

 Geocoma elegans of Heller. 



Three species have been referred to Palceocoma: — (1) P. Cunliffei, 

 Forb., based upon some indeterminable fragments ; (2) P. Fursten- 

 hergii, tolerably well known, nevertheless I dare not decide on its 



