TRIB IONE CONN “GNISU: IDRIS AON | OZ Qg 
Cy 
rostrum are partly preserved. A large elliptic subcentral node indi- 
cates the mud-filling of the aperture. The plates of the right side 
(in the drawing) show furrows which correspond to those seen on 
the surface of the lateralia in the Devonian Protobalanus 
hamiltonensis Whitfield and therefore probably indicate that 
these plates whose substance is dissolved retain the upper surface, 
while the smooth surface of the plates on the left would suggest 
the under surface of the plates. 
The lack of any substance, except a probably secondary calcareous 
film on the left side, and especially the absence of any carbonaceous 
matter, indicate that the originally conchiolinous plates of the phyl- 
locarid ancestors, were already greatly strengthened by calcareous 
deposits and consequently much thickened, as is also suggested by 
the height of the central mud-filling. 
Compared with E. informans, this form possesses a less 
elongate outline, the two diameters being subequal (1 == 12.8 mm, 
w==11.1 mm). The plates were, therefore, more subequal in out- 
line and size, excepting the elongated carina and rostrum. The most 
apparent difference rests, however, in the form of the apexes of the 
lateralia, those of this species being acute while in the genotype 
they are truncate. 
Horizon and locality. Trenton limestone, at Trenton Falls, 
Oneida county, N. Y. 
Remarks on the phylogeny of the acorn barnacles suggested 
by Eobalanus. 
The remarkable crustaceans here described are undoubtedly very 
primitive barnacles. They at once carry the Balanidae or acorn 
barnacles, hitherto traced only to the Devonian in Protobalanus 
hamiltonensis Whitfield back into Ordovician time, and also 
shed an important light on the origin of the Balanidae. 
According to Pilsbry’s authoritative view, zoologists “in the 
absence of paleaeontologic evidence,’ may assume that all acorn 
barnacles descended from a primitive stock having 8 mural com- 
partments, for the most generalized genus now existing, Cato- 
phragmus, has 8 main compartments, with numerous smaller ones 
outside, the latter representing the upper scales of the peduncle of 
pedunculate ancestral forms.’ The shell of Balanus consists of 
*Pilsbry, H. A. The sessile barnacles (Cirripedia) contained in the collection 
of the U. S. National Museum; including a monograph of the American 
species. Smiths. Inst., U. S. Nat. "Mus. bull. OR, WON, 0), Gy 
