4() 



BULLETIN 60^ UNITED STATES NATIONAL MUSEUM. 



The inf raiiiedian latiis is narrow, triangular^ with the apex strongly 

 curved toward the occludent hordei\ overlying the baso-lateral angle of 

 the scutum. A low rounded rib runs down each side. The umbo is 

 apical. 



The carinal latus is triangular, its apical half projecting free behind 

 and downward below the carina, and also flaring outward, though 

 less than in ^5'. arietiimm. The spread from tip to tip is 3.75 mm. in 

 the type specimen. 



The peduncle is clothed with rather large, narrow, transversely 

 lengthened scales, in about 8 rows of 8 or 9 scales each. 



^ b 



Fig. 14.— Scalpellum dicekatitm. a, lateral view; and />, carinal view x 3. 



Length of the capitulum 18.5, width 7.8 mm. Length of the 

 peduncle 7 mm. Length of the carina 13.5, diameter near the base 

 2.8 nmi. 



This species lives with 8. arietinuni on the spines of echinoids and 

 the arms of crinoids, in shallow or moderate depths. The two species 

 are obviously related, yet quite distinct by the difference in shape of 

 the carina and inf ramodian latus, and the terminal umbones of tlie infra- 

 median and upper latera and of the carina in S. dlceratinn.^ while in S. 

 arietinum the umbones of these plates are removed from the apices. 

 There are also some minor diflerences in other plates, readily seen in 

 the figures. The carinal latera sometimes diverge almost as widely as 

 in S. arietinum^ and much more than in the figured type. The color 

 varies from crimson to pure white. (Fig. 14.) 



