NOTES ON ECHINODERM MORPHOLOGY. 15 



Ophiomusium granosum (PI. I, fig. 7) will be universally 

 admitted ; and so, though in another way, with the curious 

 genus Ophiopyrgus. Lyman^ says of it, " With its peg-like 

 central primary plate and dome-like disk it suggests a simple- j 

 armed Criuoid whose head has been broken from the stem." 

 StuderS speaks to the same effect ; but he has been singularly 

 unfortunate in his more detailed comparison between the 

 apical plates of Ophiurids and Crinoids respectively. Adopting 

 the views of Loven and Agassiz, as modified by myself,^ con- 

 cerning the homology of the so-called " genital plates " of 

 Urchins and Starfishes with the basals of a monocyclic Crinoid, 

 he compares " die Anlage des Skeletts bei Ophiuriden " with 

 the calyx of a dicyclic Crinoid. This is, in fact, what I did j 

 myself in my fifth note,^ but our methods of procedure are j 

 radically dift'erent. ['; 



Ophiopyrgus is a genus which resembles Ophiomusium 

 pulchellum (PI. I, fig. 9) in having a dorsocentral (1) sur- 

 rounded by five radial primaries (4), but no basals. According "J 

 to Studer, "Bei Ophiopyrgus ist das Centrodorsalemit seiner 

 erhabenen Form noch dem eines ungestielten Crinoiden, etwa / 

 Haplocrinus, ahnlich. Dann folgen die radialenBasalia, die ■ 

 Radialia sind zum Terminale geworden und an der Spitze der I 

 Arme geriickt, wahrend die Parabasalia nach der A''entralseite 

 geriickt sind und zu Muudschilderu wurden. Auch hierzu 

 bietet Haplocrinus rosaceus, Roem. Analogieen, indem 

 dort die Parabasalia schon cine actinalgeneigte Stelluno- 

 einuehraen und unmittelbar die grossen Oralplatten trageu.^' 



The piece which Studer calls centro-dorsal is that termed 

 dorsocentral by Sladen and myself, the former term being re- 

 served for the top stem-joint of the Comatulae, to which it was 

 originally limited by Dr. Carpenter. This is a totally different 



' ' " Challenger " Report,' p. 33. 



- ' Uebersicht iiber die Ophiuriden welche wahrend der Keise S. M. S. 

 Gazelle um die P]rde 1S74— 1S76 gesatnmelt wurden," * Abhaudl, d. Koni^l. 

 Preuss. Acad. d. Wiss. zu Berlin,' 1882, p, 10 (of separate copy). 



3 This Journal, vol. xviii, 1878, pp. 356—371. 



* This Journal, vol. xxii, 1882, pp. 378—381. """"--v^ 



