Testa Rissoidea; nucleo magno; apertura labio producto, labro subpostice juncto, subito in adultâ contracta.
Type. Amphithalamus inclusus, Cpr. Br. Assoc. Rep. 1863, p. 656; Ann. Nat. Hist. Jan. 1865.
Hab. Santa Barbara, Jewett; S. Diego, in shell-washings. Cooper.
? Amphithalamus lacunatus, Cpr. n. s.
? A. t. adolescente “A. incluso” simili; nucleo similiter minutissime et confertissime spiraliter et radiatim striulato; sed majore, latiore, anfr. subplanatis; basi late lacunatâ, haud carinatâ; adultâ ?..
Long. 0·06, long. spir. 0·03, lat. 0·03, div. 50°.
Hab. San Pedro. Cooper.
Two dead specimens in the shell-washings of Dr. Palmer’s consignment to the Smithsonian Institute might have been passed over as the young of Barleeia subtenuis, but for the possession of exactly the same remarkable nucleus as A. inclusus. It is presumed, therefore, that they are congeneric; if so, the adult has not been seen.