184 BULLETIN OF THE BUREAU OF FISHERIES. 



is convex and the tergal straight. The plate has a dense and minute sculpture of fine radial lines 

 which arc irregular or divaricating, and a coarse sculpture of well spaced wrinkles and furrows, parallel 

 to the growing margins of the valve. The furrows and riblets arc more emphatic in the baso-carinal 

 area of the senium, being crowded there into a strong corrugation. Inside there is a single massive 

 tooth, bifid at its summit, under the umbo in each valve. 



The tergum is wedge-shaped, closely corrugated parallel to its scutal border, but. with two roundel, 

 contiguous ribs running along the opposite or outer border. The apical angle is less than 90°. Inside 

 smooth, with a minute tooth at the scutal margin of each tergum near the occludent end. 



The carina is narrow distally, but from the middle down it widens rapidly, the sides becoming much 

 broader and at the same time flaring laterally. They are corrugated parallel with the scutal margin. 

 The roof of the carina is very narrow throughout, widening graduallyand slightly upward and with a 

 median hollow or furrow. Inside there is a massive transverse septum at the lower two-fifths of the 

 carina, rising in a blunt articulating tooth at each side 



The peduncle is very short, cylindric, circularly wrinkled, covered with a tough flesh-colored 

 integument. 



Capitulum, total length 14.5, breadth (3.4, diameter 3 mm. Scutum, length 11.7, breadth 5.7 mm. 

 Tergum. length 6.2, breadth 2.2 mm. Carina, length 10, breadth 2, diameter 2 mm. Length of 

 peduncle 2 mm. 



Albatross station 4117, northwest coast of Oahu. 241 to 282 fathoms, bottom of coral sand and 

 foraminifera, in copious numbers on large spines of a sea urchin. Also station 4117, 253 to 282 fath- 

 oms, in nearly the same place. South coast of Oahu, 315 fathoms, fine white sand and mud. Station 

 3998, vicinity of Kauai, 228 to 235 fathoms. Stations 4090, 4097, 3883, and 386fi, Pailolo channel, 

 between Mum and Molokai, 277 to 304 fathoms, bottom of fine gray sand and globigerina ooze. Station 

 3839,south coast of Molokai in 259 to 266 fathoms. 



In the straightening out of the basal margin to bring il paraded to the occludent. edge, P. bdluw. is 

 like Megalasma striatum Hoek. The system of sculpture, the very short peduncle, the internal ridge 

 across the cavity of the carina, and the situs on sea-urchin spines are also features approximating Mega- 

 lasma: but that genus differs by the slightly higher position of the umbo of the scutum, on the occludent 

 margin, and the much broader crest of the carina. On the whole, P. helium may be said to stand inter- 

 mediate between Pcecilasma carinatum and Megalasma. Pcecilasma helium is an abundant species on fine 

 sand bottoms throughout the Hawaiian group, always seated on large Echinus spines, frequently sharing 

 them with Alepas. It is a handsome little barnacle, very constant in all its features. 



Dichelaspis hawaiensis n. sp. 



[PI. iv. fig. 5.] 



The capitulum is much compressed, unsymmetrically long ovate, supported on a nude peduncle 

 half the length of the capitulum or shorter. The valves arc in contact only at their ends. The general 

 integument is smooth. 



Tic scutum is L-shaped, the basal segment narrower than the occludent, the latter widening above 

 lo iis oblique termination, and about twice the length of the basal segment. The tergum is irregularly 

 triangular, with blunt apex, slightly concave and very long carina] margin, and with a notch near the 

 occludent end of the scutal margin for the reception of (he distal end of the scutum. An arcuate furrow 

 runs upward from this notch. The carina is arcuate and extends upward well beyond the middle of (he 

 tergum. It is widest in (he middle, and at. the base is expanded in a biramose appendage clasping (lie 

 top of the peduncle, which it half encircles. The peduncle is stout, cylindrical, and circularly wrinkled. 



Lenglh of capitulum, G.5 mm., breadth 3.2 nun. 



Type. no. 32409, l". S. National Museum, from Hawaiian Islands, collected by the Albatross, 1902, 

 attached toa slender gorgonian. 



This species is more closely related to D. orthogonia Darwin than to any other. It differs from that 

 in the shorter basal portion of the scutum, the simpler shape of the tergum, and the more broadly clasp- 

 ing basal appendages of the carina. "Unfortunately (he station number was not preserved, so that (lie 

 i xad location can not be given. 



