THE BARNACLES IN THE U. S. NATIONAL MUSEUM. 91 



have a minute sculpture of fine, short, diverging impressions, giving 

 the general effect of radial stria?, and coarse, wideh' spaced concentric 

 ridges. The peduncular foramen is large and cordate in shape. 



The scutum has a nearly straight occludent margin; carinal margin 

 well arched. The basal margin is straight and forms an acute angle 

 with the occludent. The basal edge flares broadl}' outward, there 

 being a deep furrow or concavity above it. A distinct ridge runs 

 almost straight from the umbo to the carino-tergal angle, dividing the 

 plate into two areas, the upper one slightly the greater. Internally 

 the scutum has no basal rib and no umbonal tooth. There is a dull or 

 liisterless band along the internal basal margin where the peduncle is 

 attached, contrasting with the glossy surface elsewhere. This band 

 is of abovit equal width throughout and has no specir.l sculpture. 

 (Plate VII, fig. 12.) 



The tergum is trapezoidal, with parallel occludent and carinal bor- 

 ders, the former dou))le the length of the latter. A furrow runs from 

 the umbo to the carino-scutal angle. 



The carina (figs. 13, 11:) is strongly arched; its roof is flat, with a 

 median depression. The sides are well developed toward the base, 

 closely striated longitudinally. On each side of the apical umbo the 

 sides are auriculate, being produced laterally and twisted, the basal 

 margin having somewhat the shape of a brace, thus: — -'— . The carina 

 does not project basal ly as far as the scutum, and its base forms only 

 the dorsal border of the peduncular foramen, not clasping the pedun- 

 cle.. When removed, the carina is seen to be concave internally. 

 From the basal margin a very short, transverse, strongly })icuspid 

 plate springs. This plate lies nearly parallel to the upper portion of 

 the carina, but makes a right angle with the umbonal portion. 



The peduncle is very short. 



Length of the capitulum 15.. 5, breadth 7.5 mm., greatest diameter 

 4 mm; length of the carina 10 mm; length of the peduncle about 2 mm. 



This species is related to M. carinatum Hoek, from near Culebra 

 and Ascension islands, but differs bj^its straight occludent margin; the 

 carina is longer, less expanded, and differently shaped basally, and the 

 basal margin of the scutum is longer and flares strongly. The detached 

 carina is shown in figs. 13, 14. 



Three examples were taken at two adjacent stations. 



MEGALASMA SUBCARINATUM, new species. 

 Plate VII, figs. 1-5. 



Type.—Q2X, No. 9059, U.S.N.M. 



Type-locaJity. — Allaiross Station 2042, east of New Jersey, 1,555 

 fathoms, on spines of a sea urchin. 



