ARBACIA SPATULTGERA. 7 



Troscliel maintains, also, Tetrapygus as a separate genus ; for reasons al- 

 ready stated * I do not think he is correct. The property possessed by the Ar- 

 baciadae of resorbing at any time during their growth the primary abactinal 

 interambulacral tubercles, and clianging them into a sort of chagrin, or finely 

 granular, nearly bare abactinal star, is not of generic value, as specimens in 

 this condition of growth are found of all sizes, up to the largest, in species 

 which Troscliel does not j)lfice in the genus Pygomma (A. stellata, A. Du- 

 fresnii, A. punctulata, A. pustulosa), and on the sti'ength of which he se2:)a- 

 rates Echinocidaris into two subgenera, which appear to me not valid, if I 

 am correct in my interpretation of the number of species. Troschel objects 

 to the identification, on geographical grounds, of A. pustulosa, A. fequituber- 

 culata, and A. loculata. I can only say I have carefully compared large 

 series of the first from Brazil, of the second from the Mediterranean, Azores, 

 and Madeira, and of the third from Liberia and Cape Palmas, and am com- 

 pelled to unite them all under one specific name. This is not the only 

 species found on the two sides of the Atlantic, common to the West Indies, 

 Brazil, Azores, Mediterranean, and Cape Verde Islands. The number of com- 

 mon species is daily increasing : compare list given in the Geographical Dis- 

 tribution of the Eevision of the Echini, Part I. p. 232, Southern Brazil to 

 Eastern Virginia ; and p. 234, Portugal to West Coast of Tropical Africa. 



San Matias Bay ; Straits of Magellan ; Eden Harbor ; Lat. 37° 42', South ; Long. 56° 20', West. 



Arbacia spatuligera 



! Echiitii^ (Afj(irites) spatuliger Val., 184G, Voyage Venus. 

 ! Arhacia Kjjalnli(jem A. At:., 1872, Rev. Ecli., Pt. I. p. 93. 



A few specimens of this species were collected by the Hassler Expedition at 

 Payta. Troschel dissents from my views in associating A. grandinosa with 

 A. pustulosa, because it is found, he says, on the west coast of South America. 

 Valenciennes's original came from Carthagena, on the east side of the Isthmus 

 of Darien, and is not to be distinguished from E. pustulosa. The confusion 

 which Troschel seeks to remedy by reconciling the synonymy with the cita- 

 tions can only be rectified from an examination of the originals. Thus there 

 is no possibility, in the case of A. Dufresnii, of mistaking Blainville's original, 

 which certainly did not come from Newfoundland. What has been called 

 E. grandinosa by various writers has undoubtedly been collected^ on the west 

 coast of South America ; but the specimens are either A. stellata or A. spatu- 



* A. Agassiz, Revision of the Eeliini, Pt. 11. 



