148 



SUPPLEMENTARY NOTE. 



Since the preceding* paper on Cryptonella, Centronella, etc., was 

 published, I have received from Dr. Rominger, a figure illus- 

 trating the interior of a specimen referred by him to Centronella 

 glans-fagea. This figure of the loop is quite different from that 

 given by Mr. Billings for Cenlronella glans-fagea, and shows es- 

 sentially the same character as that of Cryptonella. Should 

 this reference Drove to be correct, it may become questionable 

 whether the minor differences already pointed out in the C. 

 glans-fagea, and authentic specimens of Cryptonella, are of suf- 

 ficient importance to separate the two genera. It should be 

 observed, however, that at a later date (May, 1861),* Mr. Bil- 

 lings has published Centronella hecate, giving, in fig. 99 a, " a spe- 

 cimen with the dorsal valve removed, showing the loop which 

 is covered with minute crystals of silex." In this species, 

 having all the external characters of a congener of C. glans- 

 fagea, no mention is made of any difference observed in the 

 character of the loop from that published and illustrated in 

 1859. We are therefore scarcely warranted in placing in 

 the Genus Centronella species having an internal organization 

 so different as that observed in species of authentic Cryptonella, 

 until a reexamination of the original specimens of Mr. Billings 

 shall confirm his first observations, or show them to correspond 

 wijh those of the genus last named. 



Albany, February 25, 1863. 



Fig. 38. 



Centronella glans-fagea. 

 Interior showing the loop, from a figure by Dr. C. Rominger. 



* Canadian Journal, May, 1861, page 272. 



