HUDSON RIVBR BEDS NEAR ALBANY 575 



§ 3 CRUSTACEA 



Ctenobolbina. 



Several different forms belonging to this genus, which has, 

 hitherto, not been reported from this state, were found at various 

 horizons. They are: 



1 Ctenobolbina ci lata, Emmons sp. var. c o r n u t a , 

 var. nov. (see pi. 2, fig. 5-7) 



This form differs from the typical Ctenobolbina ciliata 

 in having the posterior lobe not so round and bulbous, and the 

 middle lobe produced into a long, stout, blunt spine. The latter 

 it has in common with a variety described by Ulrich {Jour, Cin. 

 soe. nat. Jiist. 1890-91. 13 :109) ae Ctenobolbina ciliata 

 var. c u r t a, from the lower (Utica) shales of the Cincinnati 

 group. It differs from this western relative in being relatively 

 longer, having the principal and posterior furrow fully as wide as 

 the type of the ispecies and poissessing a well developed frill. 

 Both forms, which occur in homotaxial beds, represent an early 

 divergence from the typical direction of development of the genus 

 by the production of an elevated process, thus forming a separate 

 section of the species; in a very similar manner as the species 

 of C e r a t p s i s , Ulrich (as Beyrichia oculifera, 

 Hall) differ from those of T e t r a d e 1 1 a by possessing an ele- 

 vated process. The remark of Mr Ulrich that these processes in 

 C e r a t o p s i s (loc. cit. p. 113) are not a " mere ornament " but 

 of a certain claesificatory value, would be also pertinent in regard 

 to the two horned varieties of Ctenobolbina ciliata; 

 and it may at some time become necessary to unite them under 

 another generic name. 



Dimensions. Length 1.45 mm, hight .80 mm. 



Lower Utica shale of Mechanicsville, Saratoga co. N. Y. Up- 

 per Utica shale of Creen Island, Albany co. N. Y. 



2 Ctenobolbina ciliata, Emmons sp. {see pi. 2, fig. 

 8, 9). 



Typical specimens of Ctenobolbina ciliata have been 

 collected at Green Island and at Menands (stations 10 and 11); 



