CRUSTACEA. 211 



plate as is characteristic of the genus Creusia. A single conspicuous furrow, 

 slightly within and concentric with the margin, may indicate the line of 

 contact of the capitulum with the walls of the basis. 



Basis tuhuliform, sub-cylindrical or cup-shaped. 



The specimen is attached to a colony of Favosites hemispkericus and has at 

 some time been overgrown as far as the aperture by the multiplication of 

 the cell tubes. A portion of the coral was subsequently removed by natural 

 causes, exposing the capitulum, but leaving the tubular basis completely 

 enveloped. The surface of the former still hears traces of the cell walls 

 of the coral. By removal of a portion of the coral near the side of the 

 specimen it is found that the internal cavity is partially filled with soft 

 decomposed chert, the remainder of the cavity filling, the capitulum and the 

 entire coral being silicified. The internal plates, scutum and tergum, are not 

 preserved. 



Dimensions. The capitulum has a length of 10 mm., and a width of 

 8.5 mm. The depth of the tubular basis can he measured through the 

 aperture for 8 mm., but is probably somewhat greater. 



Observations. This interesting species brings to our knowledge a representa- 

 tive, from Devonian rocks, of forms included under the recent genera Pyrgoma 

 and Creusia, neither of them previously recognized in palaeozoic formations, and 

 the latter not heretofore known among fossils. Features of distinctively generic 

 value in which this species differs from recent members of the genus Creusia 

 are not readily apparent, and, therefore, the term Paltzocreusiti is used tenta- 

 tively to express the probability that such differences will eventually he 

 found. 



Distribution. Corniferous limestone. LeRoy, Genesee county. 



