HIPPONOE ESCULENTA. 301 



smaller ones are found on its sides arranged >°°, so that the larger plate occu- 

 pies the base of the V-shape, and the smaller plates the point where the 

 anus opens (PL VII f. 10). This specimen measured 9.1 mm ', and had eleven 

 coronal plates ; the genital plates have become slightly more distinct. It 

 is, however, only in specimens measuring 10 mm in diameter, and having 

 fourteen coronal plates, that the abactinal system becomes more promi- 

 nent and the sutures well marked. In specimens measuring 11.2 mm " in 

 diameter the abactinal system is slightly raised, and numerous small plates 

 of anal system have appeared, completely obscuring the original arrange- 

 ment of the anal system. 



HIPPONOE. 



Hipponoe Gray, 1840. Synops. Cont. Brit. Mus. 



Echini of large size, with thin test, tubercles small and numerous, imper- 

 forate, not crenulate, arranged in horizontal and somewhat irregular ver- 

 tical rows, median ambulacral and interainbulacral spaces frequently bare. 

 Actinostome small, but deeply notched Poriferous zones broad ; pores 

 arranged in three vertical rows, middle row sporadic, exterior ones regu- 

 larly vertical. Ambulacral areas very broad. Spines short, moderately 

 stout. 



In retaining the name Hipponoe of Gray, to which objections will un- 

 doubtedly be raised on the ground of Hipponoa having been before used 

 by Audouin, and from the fact of the name alone appearing without further 

 indications of its connection, I am simply carrying out the principle that 

 Hipponoe and Hipponoa are two very different words, and that when speci- 

 mens are accessible which have served as basis for any systematic work, 

 their results should be accepted, when correct, even when they upset a 

 nomenclature generally recognized. 



Hipponoe esculenta 



! Cidaris esculenta (Leske), 1778. Addit. Klein. 



! Hipponoe esculenta A. Agass. 1872. Rev. Ech., Pt. I. 



PL VI a . f. 1-3 ; PL VIII f. 29. 



In large specimens measuring 110 mm we find twelve vertical rows of prin- 

 cipal tubercles in the interainbulacral space ; the arrangement of the tuber- 

 cles on each plate is more in horizontal rows ; towards the median line, 



