THE BARNACLES IN THE U. S. NATIONAL MUSEUM. 75 



GROUP OF SCALPELLUM GRUVELI. 

 SCALPELLUM IMPERFECTUM, new species. 



Type.— C?it. No. 32914, U.S.N.M. 



Type-locality. — Alhatross Station 2731, northeast from Hatteras, 

 north latitude 36^ 45', west lonj^itude 78° 28', 781 fathoms, seated on 

 Scalpelliwi velutmuni Hoek. 



Othe7' localities. — Cat. No. 12891, Station 2741, east of mouth of 

 Chesapeake Bay, north latitude 37° 44', west longitude 73° 57', 852 

 fathoms. Cat. No. 9007, Station 2190, north latitude 39° 35', west 

 longitude 69° 44', in 1,230 fathoms green mud, on an Echinoderm 

 spine. 



The capitulum is composed of 13 valves, those of the upper whorl 

 imperfectly calcified. The valves are joined by wide, chitinous sutures. 

 The scutal and carinal margins are regularly 

 convex throughout. The apex is obtuse. 

 The cuticle is thin and smooth, and the plates 

 are weakly marked with growth lines. 



The scutum is triangular, narrow above, 

 over twice as long as wide, with a small wing 

 or triangular projection on the lateral side 

 of the apex. The occludent margin is slightly 

 convex, longer than the straight lateral mar- 

 gin. The umbo is apical. 



The tergum is V-shaped, the two branches 

 of about equal width, and both are somewhat 

 curved. That along the occludent margin is 

 truncate at the end under the apex of the ter- 

 gum. The other branch is much longer and 

 tapers to an acute end. The apex is rather 

 strongly recurved and acute, but a chitinous 

 border projects beyond it along the occludent ^^^- so— scalpellum 

 margin, and there is a very small wing on i 

 the carinal side of the apex. 



The carina is widely separated from the other plates. It is abruptly 

 bent at the umbo, which is situated between the upper third and fourth 

 of the whole length of the plate. The roof is flat, bounded b}^ angles 

 or low ribs, and with nearly straight growth lines. The sides are 

 moderately wide in the middle, tapering above and below. The base 

 •is almost squarely truncate. 



The upper lateral plate is widely separated from the other plates, 

 piriform, narrower above, the scutal and tergal margins straightened, 

 baso-carinal margin irregularly rounded. The umbo is at the upper 

 third of the length of the plate.' 



IMPERFEC- 

 TUM. LATERAL VIEW OF TYPE X 



