312 BULLETIN m, UNITED STATES NATIONAL MUSEUM. 



deep. There is no adductor ridge. Pit for the lateral depressor 

 muscle deep. Interior white. 



Terguin with moderately developed articular ridge and narrow 

 articular furrow. Spur broad, rounded, and short. Carinal lobe, 

 bearing the crests, rather large, making an angle with the rest of the 

 basal margin. 



This species has valves much like those of the American C. fragilis, 

 but the articular ridges of both valves are weaker. It differs from 

 C. challenf/crl by the much less broadly reflexed articular ridge of 

 the scutum, the absence of an adductor ridge, and the broader lower 

 part of the tergum. It is also unlike the specimen referred to G. 

 stellaius, figured in the Siboga report, but it probably belongs close 

 to steUatus. 



Besides the type lot from Zamboanga collected by Dr. E. A. 

 Mearns, there is a beautiful group seated together with Tetraclita 

 squamosa upon a mangrove oyster collected by the Albatross in the 

 Philippines, exact locality not noted. The specimens were preserved 

 dry, and I have. not worked out the mouth parts and cirri. 



CHTHAMALUS WITHERSI, new species. 

 Plate 73, figs. 2 to 2c. 



• Type.— Cat No. 48088, U.S.N.M. 



Locality. — Reef opposite Cebu, Philippine Islands, in a group of 

 Balanus amphitrlte. Albatross., April 7, 1908. 



Specimens not distorted by crowding are depressed with a rather 

 large, wide orifice ; cinnamon brown, becoming bluish where the epi- 

 dermis is worn off; the surface smooth, but little worn, the lower part 

 showing growth-stria). Ala) broad, with arched, subhorizontal sum- 

 mits, and sculptured with growth-strire stronger than on the parietes. 

 Interior smooth, without basal rugosity or inwardly growing ledge, 

 dull brown, shading into white; sheath short. Sutures smooth, not 

 plicate or crenulated. Diameter, 9.5 mm. ; height, 3 mm. 



The scutum is thin, triangular, convex between apex and base, more 

 than twice as long as wide, the basal margin somewhat surpassing 

 the tergal. In the lower part there are fine groAvth-lines. Inside dull 

 brown and white, smooth. The articular ridge is a very feebly de- 

 veloped median lobe, not extending beyond the scutal border. The 

 articular furrow is shallow but sharply incised. There are no pits 

 for the adductor or depressor muscles. 



The tergum is very narrow, club-shaped, very thick (not eroded in 

 the specimens seen). The articular ridge is rather high but not 

 much reflexed. Articular furrow shallow. The lower half of the 

 valve is narrow, but thick, very convex externally, forming a sort of 



