SOME WEST INDIAN ECHINOIDS. 11 



size of about 25 mm. horizontal diameter. It must, however, be admitted that this 

 tubercle (and its spine) is sometimes very small and inconspicuous, even in the 

 larger specimens. The number of coronal plates is virtually the same in both species. 

 The apical system and peristome do not seem to afford any constant differences 

 from St. affinis in structure or size. The radioles, on the other hand, afford a con- 

 sjncuous ilifference through their greater length, more than twice the horizontal 

 diameter of the test in grown specimens. This, it is true, may also be the case 

 in St. affinis, as pointed out by Clark (The Cidaridse, p. 20.3), but, so far as I have 

 been able to find, only in the young specimens; in those fully grown specimens which 

 I have seen they do not exceed one and one-half times the horizontal diameter. 

 The structure of the radioles also differs somewhat in the two species. In St. 

 lineata the hairs covering the ostracum are irtore slender than in St. affinis and 

 they are not anastomosing (Plate 16, fig. 9), while in St. affinis they are generally 

 somewhat branched and may form anastomoses (see /ngfo(/' Echinoidea, pt. 1, pi. 

 11. fig. 1; the statement made there, p. 36, that they do not form anastomoses, 

 does not always hold good). The radioles are beset with numerous small, longi- 

 tudinally arranged spinelets as in St. affinis. The secondary spines do not differ in 

 length or shape from those of St. affinis, only the "ampullae" are, perhaps, somewhat 

 larger than in that species. 



The globiferous pedicellariaj do not present any distinct differences from those 

 of St. affinis; the tridentate pedicellari^, on the other hand, are characteristically 

 different, as is best seen on comparing the two figures 4 and 14, Plate 17, represent- 

 ing a tridentate pedicellaria of each of the two species. The space between the 

 valves is distinctly narrower in lineata than in affinis; and the basal part of the 

 valves is also different in outline. They are considerably larger in St. lineata up 

 to about 1.5 mm. length of head, whereas in St. affinis they scarcely exceed 0.8 

 mm. The spicules are alike in both species. 



The color is white; against this ground color the brown median ambulacral 

 and interambulacral line (to some extent also the horizontal interambulacral 

 sutures), and a brown band over the middle of the genital plates, making a con- 

 spicuous ring on the apical system, stand out very beautifully. The secondary 

 spines are wholly white; tiie radioles are also mostly white, but they may some- 

 times show a faint reddish tint, especially near the tij); there may even be traces 

 of bands of this color. 



I dredged this species (2 specimens) in about 250 fathoms off Frederiksted, 

 Santa Cruz (Danish West Indies), in January, 1906. In the U. S. National 

 Museum I have seen additional specimens of it from off Havana, taken by the U.S. 

 fisheries steamer Albatross in 1SS6, besides several more specimens from stations 

 2135 (Cat. no. 10753). 2152 (Cat. no. 7485), 2154 (Cat. no. 7476), 2157 (Cat. no. 

 7478), 2162 (Cat. no. 74S2), 2319-24, 2327, 2336-37, 2342, 2345-49 (Cat. nos. 

 10709-10). The.se sjjecimens are mentioned in Doctor Rathbun's Catalogue of 

 the Collection of Recent Echini in the U. S. National Museum, page 260, as Doro- 

 cidaris papillata; on the labels of most of them, iiowever, is found a question 

 mark indicating that Doctor Rathbun was doubtful whether they were correctly 

 referred to that si)ccies. The species evidently must be rather common in the West 

 •26599°— Bull. 74—10 2 



