158 HYATT, 



very full list of species had been consulted ; but the re- 

 sults so much surpassed my anticipations, that I have 

 given it now, hoping the logical sequence of the whole,, 

 rather than the perfection of the details, would justify its 

 introduction in this place. 



The genus Lophopus i& omitted with the exception 

 of the "Ccenrecial Characters," which are quoted from 

 various European authors, every effort on my part to find 

 or obtain a single specimen having been unsuccessful. 

 Nevertheless, the Pectinatella on one side, and the Pluma- 

 tella on the other, show very plainly that it must have an 

 intermediate character with regard to the polypide and 

 the parts omitted. The following pages are intended as- 

 an explanation of the characteristics noted in the table,, 

 and should be read in connection with it. 



CGENCECIAL SYSTEM. 

 CCENCECIUM. 



Single or radiatory. The young colony of any one 

 species of Fredericella may have (1) two or more poly- 

 pides growing in opposite directions and simultaneously 

 branching, or (2) they may spring from one polypide 

 alone. (1) In this way a colony arises growing equally 

 from the centre, with at least two compound branches, 

 the polypides turning the open side of the lophophoric 

 crescent toward the centre, and is truly radiatory. (2) 

 By the last method, however, only one compound branch 

 is formed, and the colony is one-sided or single. Freder- 

 icella Walcotii has, perhaps, fewer radiatory colonies 

 than any other species of that genus, Fredericella Pul- 

 cherrima and Fredericella regiua being very generally 

 radiatory. There are, nevertheless, many single colonies 

 in both of the last-named species, but they are not so fre- 

 quently met with as the truly radiatory coenoecia. 



The single colonies mingle more or less with the radi- 

 atory in all four of the American Plumatellas. The first 

 are most numerous and constant in variety a of Pluma- 

 tella vitrea. 



All the figures of Lophopus crystallinus are radiatory, 



