20 



NATURAL HISTORY BULLETIN 



sented in the present collection by 14 specimens, most of which 

 are however quite young. I am satisfied that Mortensen's insti- 

 tution of a new genus, Stylocidaris, for this species and its near 

 allies is advisable and I am inclined to think that his suggestion 

 that ajjinis hybridizes with Tretocidaris hartletti is worthy of 

 serious examination. Several of the specimens in the series be- 

 fore me have distinctly banded spines as in T. hartletti but their 

 pedicellarae are those of affinis. They are however quite small 

 and the banded spines may be merely a revelation of an ancestral 

 character or they may indicate only individual diversity. The 

 large specimen figured by me as T. hartletti (1907, Bull. M. C. Z. 

 51, pis. 8 and 9) which showed pedicellariae in part like hartletti 

 and in part like affinis is much more probably a hybrid, as Mor- 

 tensen suggests. 



As regards Dr. Mortensen's proposed species Stylocidaris 

 lineata (1910, Bull. 74 U. S. Nat. Mus., p. 10), I have examnied 

 not only the series before me now, but the large series in the M. 

 C. Z. collection, in the hope of confirming my Danish friend's 

 judgment. I am obliged to say however that I do not find the 

 characters given at all constant. The color is the best of these, 

 and uniformly white specimens might perhaps bear the varietal 

 name lineata, if the color in life is similar to that shown by the 

 preserved specimens. If, however, there is more or less of a red- 

 dish tinge in life, the variety would be difficult to maintain. As 

 regards the tuberculation of the ambulacra and the length of the 

 radioles and trident ate pedicillarise the light and dark colored 

 forms are not separable. 



In the "Narrative" (p. 173) this species is reported naturally 

 as Dorocidaris papillata A. Ag. and is said to occur on. the Pour- 

 tales Plateau ''in definite spots where there were innumerable 

 individuals. ' ' These ' ' repeatedly came up on the tangles by the 

 hundred and became a sore trial to our patience, the serrated 

 spines being especially difficult to disengage from the tangles. 

 Indeed, this labor became one of our main occupations while on 

 the Pourtales Plateau. ' ' The specimens sent to me are from the 

 following stations: 



Station 4. Cuba: off Havana, 110 fms. 1 small specimen 

 with banded spines. 



