132 Natural History Bulletin. 



the arms bearing distant annulations. Ophiothrix orstedii 

 Liitken is the most beautiful as well as most abundant species 

 of Ophiuran at the Tortugas. The bod}' color is green or 

 blue, the arms being crossed by pure white lines, disk beset 

 with long glassy spines, and the spines of the arms bearing 

 the characteristic spinelets of this genus. Ophiornyxa jlacclda 

 Liitken is also common. The ra3's are shorter than in typical 

 specimens, and annulated with dark olive and light buffy in 

 several of our specimens from that locality. 



A species of basket-fish was collected here; Astrophytou 

 costosiiin Seba is of a purplish brown color, with very prominent 

 radial ribs bearing rounded nodules or blunt spines. The 

 branching of the ravs is not truly dichotomous except the first 

 few basal forkings. After this the main branches run straight 

 outward, giving off branchlets from time to time that are them- 

 selves truly dichotomous. Twenty forkings can be counted 

 in one specimen, and this would give, according to the method 

 of computation adopted in the famous communication from 

 Gov. John Winthrop to the Roval Society, about 21,000,000 

 terminal tendrils or branchlets. Of course a vast majority of 

 these are usuall}- lacking in museum specimens, but there are 

 still enough to hopelessly entangle the mass. The arms are 

 closely and evenly granulated throughout, and do not have the 

 appearance of segmentation so strongly marked as does 

 Astrophyton agassizii of Lyman. Radial dark, almost black 

 blotches are symmetrically placed between the radial ribs, and 

 there is a large black blotch at the centre of the disk. 



The sea-urchins were numerous individually, but the num- 

 ber of species was not remarkably great. Cidaris tribidoides 

 Bl. was found principalh' on the mud-flats just inside the reef. 

 The s\mmetrical disposition of the spines of this species and 

 the well marked tubercles make it an excellent one for class 

 use in a preliminary study of the Echini. B3' far the most 

 conspicuous echinoderm was Diadema setosum, Gray which 

 was abundant on the sand-flats near Garden Key. The spines 

 of this species attain a length of seven inches, and are literall}' 

 as sharp as needles. Although they appear to be as brittle as 



