218 HYATT, 



species, as well as in the different species and genera, may- 

 be seen by comparing them. Those figured in the plates 

 are not sufiiciently accurate. 



FREDERICELLID^ . 



Coenoecium attached, dendritic. Lophophore oval. 

 Statoblasts bare and smooth. 



FREDERICELLA. 



Coenoecium composed of elongated cells covered by 

 a thin cctocyst. Invaginated fold broad, with numerous 

 rows of posterior retentor muscles. Posterior attachment 

 of oesophageal retractors solid. 



Fredericella Walcottii Hyatt. 



This species differs from all others of the same genus 

 iij its peculiar mode of growth. The main branches are 

 closel}^ attached to the surface, and the free parts of the 

 cells or branches rise abruptly from them. The former 

 are long single stems, growing at acute angles, and often 

 crossing each other. 



There are two well-marked varieties, a and h. 



All the branches of variety a were single and closely 

 attached throughout, the only free parts were the upper 

 portions of the cells. These might be of extreme length 

 or qidte short, the attached part varying between 12 m. 

 m. and 5 m. m. the free portions between 6 m. m. and 

 1 m. m. The constant attachment and rarity of the 

 branches, together with the length of the attached part, 

 gives them the aspect of true stolons, the free portions of 

 the cells appearing like individual zooids (PI. 15, fig. 

 2). The branches of variety b still have the stolon-like 

 aspect of variety a, but the deep channels in the surface 

 of the wood prevent them from crossing each other to any 

 great extent. The free portions of the cells also fre- 

 quently branch, and the growth is then more dense than 

 in varietv a. Statoblasts were not observed. 



