48 BULLETIN 60, UNITED STATES NATIONAL MUSEUM, 



(Id. Rostrum wanting or represented by a linear rudiment. 



e. Uml^o of carinal latus at baso-carinal angle S. antlUarum. 



ee. Umbo of earinal latus at the middle to lower fourth of its carinal mar- 

 gin; carinal aspect of carinal latera radially ribbed. 

 /. Carina with ribs bounding the flat roof; umV)o of carinal latus at the 

 lower third or fourth. 

 g. Entire carinal latus sculptured with radiating riblets; growth-lines on 

 roof of carina V-shaped; umbo of ui)per latus terminal at scuto- 



tergal angle S. semiscvlptwn. 



gg. Only the basal ai'eaof carinal latus radially sculptured; growth-lines 

 on the roof straight; umbo of upper latus not terminal. 



S. mirwiUii. 



ff. Carina angular at the sides of the flat roof; umbo of carinal latus near 



middle of its carinal margin; carinal latera meeting in a rather long 



zigzag suture below the carina; rostrum linear; occludent margin 



straight -S'. gakvpaguimm. 



(IROUP OF 8CALPELLUM IDIOPLAX. 



Infraniedian latus hourglass- or wineg'lass-shaped, the umbo median 

 or below, at the contracted part of the plate. 



SCALPELLUM PROXIMUM Pilsbry. 



1907. Sralpellum proximum Pilsbky, Bulletin of the Bureau of Fisheries, XXVI, 

 p. 197, jjl. VI, figs. 9-11. 



Ty2je.—Osii. No. 324:22 U.S.N.M. 



Type-locality. — Vicinity of San Diego, California, in 1,()U0 fathoms. 



SCALPELLUM IDIOPLAX, new species. 



Tijpe.—C'Ai. No. 7843, U.S.N.M. 



Tyjye-localUy . — Alhatross Station 2140, Caribbean Sea, north latitude 

 17° 36' 10", west longitude 76° 46' 0.5", in 966 fathoms, sand. 



Other loeallt/es.— Cat Nos. 11530 and 1 4:5 5S, Albatross Station 2656, 

 between Bahamas and Cape Fear, North Carolina, in 572 fathoms. 



The capitulum is twice as long as wide, widest in the middle, taper- 

 ing toward summit and base. The ventral and dorsal margins are 

 about equally convex. It is composed of 13 fully calcified plates. 

 The cuticle is very thin and smooth. The plates are sculptured with 

 unequal lines of growth and fine, low, radial striae. 



The scutum is more than twice as long as wide. The occludent 

 margin is convex; basal and upper margins nearh^ straight, oblique. 

 The lateral margin is irregular. It projects in an angular lobe at the 

 upper lateral angle, and is deepl}' excavated below the lobe for the 

 reception of the apex of the upper lateral plate. The apex is 

 acuminate. 



The tergura is decidedly longer than the scutum, triangular, the 

 occludent margin slightly convex, the basal a trifle concave, and the 



