SYSTEMATIC DESCRIPTIONS CIDAROIDA. 19 



Academy of Sciences, the Porto Rican Government and the American 

 Museum of Natural History cooperating. A Cidaris spine closely 

 similar occurred in the Miocene, Gurabo formation at Rio Mao, half 

 a mile above ford at Cercado de Mao, Dominican Republic, T. W. 

 Vaughan and C. W. Cooke collectors, one spine, U. S. Geol. Sur. 

 station 8519. 



Cidaris species b. (Text-figures 2, 3.) 



The following is a description of these specimens : 



Spines small, cylindrical, tapering gradually from above the collar, or 

 contracted above the collar and thence tapering distally. Both specimens 

 are complete proximally, showing the milled ring and collar, but wanting 

 at the distal tip. Thickly and irregularly set with thornlike spinelets 

 which stand out nearly at right angles to the axis, or with fewer and larger 

 spinelets, which again are nearly at right angles to the axis. The specimen 

 with smaller and numerous spinelets and which is nearly complete distally, 

 measures 15 mm. in length by 3 mm. in its greatest diameter. The one 

 with two large spinelets, which is larger, is of undeterminate length, but 

 measures 3.5 mm. in diameter. 



This species is quite distinct from any other 

 known, living or fossil, in the West Indies. It 

 can be compared, however, very closely with 

 Goniocidaris biserialis Doderlein (1887, Die 

 Japanischen Seeigel, Stuttgart, plate 5), which 

 has similar and very variable spines. It is in- 

 teresting that 3 species of fossil Cidaris in the 

 West Indies, C. peloria, C. foveata, and the 

 present one, find their closest analogy in Recent 2, 3. Cidaris sp. b. 

 Eastern Pacific forms. Spines, x 2. 



Geologic age not known, Arecibo limestone, 



weathered marl, Government Road, Aguadilla to Rincon, Porto Rico, 

 km. post 2, from roadside grottoes where road-metal had been taken 

 out, 2 specimens, station 117, American Mus. Nat. Hist. No. 18566, 

 C. A. Reeds collector, Expedition of New York Academy of Sciences, 

 the Porto Rican Government and the American Museum of Natural 

 History cooperating. 



Cidaris loveni Cotteau. 

 (Plate 1, Figures 8 to 10.) 



Cidaris loveni Cotteau, 1875, Kongl. Svens. Vet. Akad. Handl., vol. 13, No. 6, p. 10, plate 1, 

 figs. 11 to 14. Guppy, 1882, Scient. Assoc. Trinidad, Proc., part 12, p. 195. 



The following is an extract from the original description of this 

 species : 



This species is of medium size, subcircular, slightly pentagonal, nearly 

 equally flattened above and below. Ambulacral areas sunken, relatively 

 wide, subundulate, nearly straight dorsally and ventrally. Pores oval, 

 very open, disposed nearly horizontally, each pair separated by a transverse 

 swelling, at first sight like the pores of Rhabdocidaris, but this resemblance 



