SYSTEMATIC DESCRIPTIONS — CLYPEASTRINA. 35 



mm. in width. A larger and very perfect specimen (No. 115376) from 

 Anguilla measures 25 mm. in height, 100 mm. in length, and 84.5 mm. 

 in width. Clypeaster concavus is very near to C. rosaceus, but in the 

 latter the petals are always well open, often very widely so, while the 

 test is usually at least one-third as high as it is long. In concavus, 

 however, the petals are nearly closed and the test is not one-third as 

 high as it is long. There are small (young) specimens of rosaceus that 

 are very close to concavus, which suggests a genetic connection between 

 the species. Cotteau's figures show the petals in concavus more widely 

 open and blunter than they are in the specimens. This species has been 

 found at a number of localities in the West Indies and is represented by 

 many specimens in the U. S. National Museum. 



A small specimen of this species, collected at Arroyo Blanco, near 

 Cevicos, Dominican Republic, by Messrs. Cooke and Ross, is of 

 interest as being a four-rayed individual. There are 4 petals dorsally 

 and, as far as can be made out, the specimen is completely four-rayed 

 throughout (plate 2, fig. 12). This tetramerous variant falls under the 

 system No. 4, in Jackson's study of tetramerous Echini (Phylogeny 

 of the Echini, p. 38). 



Oligocene, Anguilla formation, island of Anguilla, Guppy collection, 



1 specimen, U. S. Nat. Mus. No. 115373. Anguilla, Guppy collection, 



2 specimens, labeled C. ellipticus Mich, — concavus Cotteau, U. S. Nat. 

 Mus. No. 1 15374. Anguilla, Guppy collection ex Cleve, cotype, labeled 

 as original of Cotteau's plate 2, figures 4 to 8, U. S. Nat. Mus. No. 

 115375. Anguilla, Guppy collection ex Cleve, cotype, U. S. Nat. Mus. 

 No. 115376. Cotteau mentions, besides the Cleve collection, having 

 material from the museums of Stockholm and Upsala. Anguilla, 

 Guppy collection, bearing the original label C. ellipticus and on the 

 reverse C. concavus, U. S. Nat. Mus. No. 115377. 



Oligocene, Anguilla formation, Crocus Bay, roadside descent to 

 Crocus Bay from Valley, Anguilla, T. W. Vaughan collector, 1914, 1 

 specimen, U. S. Geol. Sur. station 6893. Crocus Bay Bluff, southwest 

 side, 125 feet above sea-level, Anguilla, T. W. Vaughan collector, 1914, 

 2 specimens, U. S. Geol. Sur. station 6967. Anguilla, several speci- 

 mens, British Museum, reported on by Lambert. Arroyo Blanco, 

 Cevicos limestone, near Cevicos, Dominican Republic, Cooke and 

 Ross collectors, 1 four-rayed specimen, U. S. Nat. Mus. No. 328233, 

 and 4 fragments, U. S. Geol. Sur. station 8598. Jique de la Argolla, 

 Rio Seco de San Antonio, Guantanamo, Cuba, C. T. Ramsden collec- 

 tion, 1 young specimen. Limestone escarpment northwest of Utuado, 

 Porto Rico, Arecibo formation, H. E. Anthony collector, 2 specimens, 

 station 554, Expedition of New York Academy of Sciences, the Porto 

 Rican Government and American Museum of Natural History 

 cooperating. 



Gregory reports having this species from Antigua. Dr. A. P. 



