ARBACIA SPATULIGERA. 403 



species. The original specimens of Lamarck, though slightly worn, are iden- 

 tical with the Brazilian variety of A. pustulosa, which I formerly attempted 

 to distinguish from A. aequituberculata, the common Mediterranean species. 

 Specimens of this species are said by Desmoulins to have been introduced in 

 La Rochelle on the bottom of vessels ; they are most similar to the Liberian 

 specimens, the spines of which are frequently tipped with yellow. 



Mediterranean ; Liberia ; Brazil. 



Arbacia spatuligera 



\ Echinus spatuliger Val., 184G, Voyage Venus. 



\ Arbacia spatuligera A. Ac, 1872, Rev. Ecb., Ft. I. p. 93. \Pl XXX Y.f. 7. 



This species is intermediate between A. nigra and A. pustulosa. It has, 

 like A. pustulosa, narrow interambulacral coronal plates, and but one hori- 

 zontal row of primary tubercles on each plate ; the rest of plate is covered by 

 uniform miliaries, except a small part of the younger plates near the abac- 

 tinal system, which is left bare, as in A. stellata, A. punctulata, but, of course, 

 much smaller; it has, like A. nigra, the primary tubercles placed near the 

 lower suture of the coronal plates. The genital plates are not of equal 

 size ; they diminish rapidly in size as they are placed nearer or farther 

 from the madreporic body. The ocular plates are in contact with the anal 

 system, but the genital ring is not as narrow as in either its nearest allied 

 species, resembling more the genital system of A. punctulata : in younger 

 specimens frequently only one ocular plate reaches the anal system, opposite 

 the genital plate carrying madreporic body, the other gradually approaching 

 it, with increasing size. 



There is a marked difference in the size of the primary tubercles above 

 and below the ambitus. The tubercles of the actinal part of the test are 

 largest near the ambitus, decreasing rapidly in size towards the abactinal pole, 

 and slowly towards the actmostome, forming on the actinal part of the test as 

 many as eight to ten irregular vertical rows, decreasing in number towards 

 the abactinal pole, leaving the small, bare, abactinal median part of the 

 interambulacral space flanked by three to four vertical rows of small primary 

 tubercles, with a larger vertical row adjoining the poriferous zone. On the 



