THE r.ARNACLES TN THE U. S. NATIONAL MUSEUM. 



17 



SCALPELLUM GIBBUM. new species. 



T(/pe.—Csit. No. 10060, U. S. N. M. 



Type-locality.— AlhatrosK Station 2388. Gulf of Mexico. North 

 latitude 29° 24' 30", west longitude 88° 01', 35 fathoms. 



The capitulura is subtriang-ular, the ventral margin straight, the 

 dorsal (carinal) margin angularl}^ bent in the middle; composed of 14 

 fully calcified plates, separated by -rather narrow chitinous sutures; 

 covered with a thin, rather sparsely hairy cuticle. The plates are 

 very lightly marked with growth lines. 



The scutum is more than twice as long as wide, with the umbo 

 slightly prominent, at the upper third of the occludent margin. The 

 tergal margin is very oblique; the lateral margin is angular below its 

 middle, the basal margin slightly concave. 



The tergum is very mu<'h longer than the scutum, narrowly trian- 

 gular. The occludent margin is slightly 

 convex, becoming a])ruptly and very 

 strongly recurved at the summit. The 

 scutal margin is nearly straight. The 

 carinal margin is composed of two con- 

 cave curves, a very short one above the 

 summit of the carina and a much longer 

 curve below it. 



The carina is very prominently angu- 

 lar near the middle, the dorsal outline 

 straight above the angle, a little con- 

 vex below it. The roof is convex, but 

 bounded by low lateral ribs, accom- 

 panied at a little distance by a second 

 arcuate rib on each side. The sides 

 are wide and flat, marked with four or 

 five wrinkles parallel to lines of growth. The umbo is close above 

 the dorsal angle of the valve. The upper end of the carina is above 

 the upper third of the carinal margin of the tergum. 



The upper latus is rhomboidal, the scutal and carinal margins con- 

 vex, the tergal margin straight, and the basal margin concave. The 

 umlro lies near the scutal margin, about midwa}^ between the basal 

 and tergal borders. 



The rostrum is narrow, parallel-sided, the beaks of the rostral latera 

 meeting over it above the middle. The rostral latus is shaped like the 

 brachiopod TJngula; twice as long as high. Umbo acute. Upper 

 and ])as;d margins are parallel, the lateral margin straight. 



The inframedian latus is convex, pentagonal, very much larger than 

 the other plates of the lower whorl, and fully equal to the upper latus 

 in area. Its V)asal and rostral margins are shorter than the others, 

 4715— Bull. 60—07 2 



Fig. 4.— SCALPELLUM UIBBUM. a, LATERAL 

 VIEW X 4J; h, DETAIL OF ROSTRUM. 



