204? BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



from bartletti, for no characters are given which do not, occur in some specimens 

 of that species; the other, spinosa, may prove to be a valid species, but its affinities 

 cannot be determined from the published description. The largest specimen of 

 bartletti in the collection of the Museum of Comparative Zoology is 49 mm. h. d. ; 

 another (Plates 8 and 9), not quite so large (47 mm. h. d ), has the longest spines 

 93 mm., nearly all cylindrical and not at all thorny. The test of these specimens 

 is brown, varying from fawn-color to deep red-brown, or even deep red on the 

 abactinal system. In the National Museum there is a magnificent specimen of 

 bartletti 68 mm. in diameter. This species is known only from the West Indies 

 in 88-397 fths. 



Tretocidaris panamensis. 



Dorocidaris panamensis A. Agassiz, 1808, Bull. M. C. Z., 33, p. 73. 



Plates 1, 2, Pan. Deep Sea Ech., A. Agassiz, 1904. 



This handsome species is the Pacific representative of T. affinis, but is quite ob- 

 viously distinct. The tridentate pedicellariae are wanting in all of the thirteen 

 specimens examined, of which the largest is 35 mm. h. d. The geographical range 

 of panamensis seems to be limited to the west coast of Central America and around 

 Cocos Island, in G6-1J2 fthms. 



Tretocidaris dubia, sp. nov. 



Plate 6, figs. 3 and 4. 



Test somewhat flattened ; vertical diameter about .52 h. d. ; coronal plates 6 ; 

 areolae distinct and not very deeply sunken ; median interambulaeral area not 

 sunken, very sparsely covered with tubercles, only 6 or 7 on each coronal plate in 

 addition to the scrobicular circle; ambulacra wide, nearly .40 of interambulacra ; 

 poriferous zones broad and little sunken ; median ambulacral area with a double 

 series of rather large tubercles on each margin, with space between perfectly bare ; 

 pores slightly oblique, rather large. Abactinal system .45-.50 h. d., nearly circular, 

 and clearly defined, elevated at centre, very sparsely covered with small secondary 

 spines ; genital plates rather large, higher than wide, with pores near outer edge ; 

 ocular plates more or less triangular, one (right anterior) or more excluded from 

 anal system, which is about one-half of abactinal system and lias an outer series of 

 7-10 rather large plates and 9-12 smaller ones at centre ; all plates of abactinal 

 system carry a few rather coarse tubercles of nearly uniform size ; each genital 

 plate has 14-20 ± such tubercles and each ocular, 8-12 ±. Actinostome slightly 

 smaller than abactinal system, not at all sunken, closely covered with stout plates, 

 3 or 4 in each interambulaerum and about 8 or 9 pairs in each ambulacrum. 

 Primary spines short, about equal to h. d., nearly cylindrical, seldom tapering, but 

 often truncate or slightly flaring at tip, covered with 12-13 low, longitudinal series 

 of coarse, sometimes sharp granules; actinal primaries much as in Cidaris and 

 usually longitudinally ridged at tip ; secondaries long and narrow, flat and slightly 

 widened at tip. Pedicellariae not peculiar; large and small globiferous, as in 

 panamensis ; tridentate much as in affinis. General color of test decidedly greenish, 

 especially abactinally, but anal system reddish-brown; miliary and secondary 



