210 PALAEONTOLOGY OF NEW YORK. 



type specimen has been broken away, removing the summits of the posterior 

 plates and covering the spot where the scutum and tergum would normally lie. 

 The specimen, which retains the replaced substance of the original shell, 

 shows an expanded margin about a portion of the periphery, and this prob- 

 ably represents a portion of the edge of the valves which has been flattened 

 and creased by compression. 



Dimensions. Length 4.5 mm., greatest width 3.5 mm. 



Observations. This minute species is the only known representative of the 

 Balanoid cirripeds in the Palaeozoic rocks, with the exception of Balanus carbo- 

 narius, Petzhold, from the Carboniferous rocks near Dresden, Saxony (Neues 

 Jahrb. fur Min., etc., 1842). Protobalanus, however, differs essentially from 

 other forms which are included in the order Balanidcz in its great number 

 (twelve) of plates, the usual number being six, four or one. This fact is not 

 without significance, as it may indicate a --eater specialization and a higher 

 degree of structural development than in the other fossil and recent species of 

 this order. 



Distribution. Hamilton group. In the Marcellus shales: Avon, Genesee 

 county. 



P A L M C R E U S I A, n. g. (J. M. C). 

 Pal^ocreusia Devonica, n. sp. 



PLATE XXXVI, FIGS Jl 6 



Capitulum ovate iii outline, patelliform ; length to greatest width as 5 to 4. 

 Surface gently conical, slightly depressed on the posterior slope. The apex 

 is truncated by a horizontal plane, forming a relatively large central aperture 

 bavin,-; approximately the outline of the shell itself, and a length equal to 

 one-third thai of the shell. 



The substance of the shell is apparently thin; its surface marked by 

 faint radiating striae or elevated lines. There is no apparent evidence of 

 the separate original plates, all having been coalesced into a single external 



