202 HYATT, 



In 1837, Gervais divided the Polyzoa into two sub- 

 classes, "Polypiaires hypocrepia," and "Polypiaires infun- 

 dibulati." The first included the genera with lateral arms, 

 and the second those with round lophophores, among 

 which he placed Fredericella.* 



In 1848, Fredericella was restored to its proper division 

 by Dumortier and Van Beneden, but they committed the 

 mistake of uniting it with Paludicella, a genus with a truly 

 orbicular lophophore, and devoid of an epistome.f These 

 authors, also, recognized the Hypocrepian division, as limit- 

 ed by Gervais, separating Fredericella and Paludicella as 

 a distinct group. 



Professor Allman in 1856 instituted the order Phylacto- 

 laemata, basing it upon the epistome, which is present in 

 all the genera.J 



He divides the order into two suborders ; Lophopea and 

 Pedicellinea, the former including all the Hypocrepian 

 forms, and the latter the marine genus Pedicellina. Al- 

 though differing from Professor Allman in my estimation 

 of the relations of Pedicellina, I have retained his name 

 for the Fresh-water genera, from Fredericella to Cristatella 

 inclusive. 



In the Suborder Lophopea, he has two grand groups, or 

 families, founded upon the characteristics of the cjence- 

 cium ; one the Cristatellidae, for the genus Cristatella with 

 its locomotive coenoecium ; and the other the Plumatellidse, 

 embracing all the remaining genera, that have rooted 

 coenoecia. 



There is a partial coincidence between Professor All- 

 in an ? s classification and the one I advocate. He makes 

 of his Plumatellidas two groups ; one equivalent to my first 

 family including Fredericella, because of the obsolete 

 arms, and another including precisely the same genera as 

 my second family. Thus the classifications virtually agree 

 in regard to the number of the principal groups, although 

 not with regard to their relative values. 



*GKKVAIS. Recherches sur les Polypes d'eau douce. Annales des 

 Sciences Naturelles, 2d Ser. Vol. 7, p. 77. 



tDuMOUTiER & VAN BENEDEN. Memoirs de 1'Acad. Hoy. de Bel- 

 gique. Vol. 21, p. 6. 1848. 



J ALLMAN. Fresh-water Polyzoa. p. 10. 



