MOIRA. 615 



MOIKA. 



Moera (Mich.), 18.">o. non Leach nee Hubn. 

 Moira A. Ao., 1872, Rev. Ech., Pt. I. p. 146. 

 (See Part II. p. 3G5.) 



Moira atropos 



! Spatanyus atropos Lame:., 181G, An. s. Vert. 

 ! Moira atropos A. Ag., 1872, Rev. Ech., Pt. I. p. 146. 

 (See Part H. p. 365.) 



PI. XXIII. 



West Indies ; North and South Carolina. 



Moira clotho 



! Moera clotho Mich., 1855, Rev. Mag. Zobl. 



! Moira clotho A. Ac, 1872, Rev. Ech., Pt. I. p. 147. 



There are, in the Jarclin des Plantes, and in the collection of Michelin, now 

 in the Ecole des Mines, specimens of a species of Moira most closely allied to 

 the West Indian Moira atropos ; this, and Hipponoe depressa, are the two 

 species of Echini from the two sides of the Isthmus of Panama, which it is 

 most difficult to discriminate satisfactorily, and for which more abundant ma- 

 terial is needed for an accurate comparison. The points of difference consist 

 in the different positions of the apical system, which is more central in the 

 California species ; the shorter longitudinal diameter compared to the trans- 

 verse, and, consequently, the broader and comparatively larger actinal plas- 

 tron ; the greater size of the actinostome, and the smaller anal system, which 

 is more circular, only pointed at the lower extremity. These are characters 

 which, as far as the material from the East Coast can furnish any data, ap- 

 pear tolerably uniform in the specimens I have had to examine and compare 

 from different localities. 



Gulf of California. 



Moira stygia 



! Moera stygia LiJTK., 1872, in A. Ac, Bull. M. C. Z., III. 

 ! Moira stygia, A. Ac, 1872, Rev. Ech., Pt. I. p. 147. 



This is a most characteristic species, and at once distinguished from its con- 

 geners by striking features. The test is remarkable for its great height, 

 its general conical form, and the sharp, slightly rounded posterior keel, ex- 

 tending from the vertex to above the anal system, — the vertex is about half- 

 way to the posterior edge from the apex, along the arched keel, — its elon- 



