90 VINE : BRITISH PALEOZOIC CTENOSTOMATOUS POLYZOA. 
features about the " ornamentation " of the vesicles of the Devonian * 
forms that are not found in the Silurian, it will I think be far wiser 
to keep the two forms distinct. If, however, we accept the Silurian 
species as types of fossil Ctenostomata, A. stellatum must be accepted 
also as an ally, especially so as the authors say " the clusters are 
connected together by creeping filamentous tubes, the free surfaces of 
which are perforated by a single row of minute foramina, and which 
generally anastamose so as to form a network." 
Not very rare in the Hamilton formation (middle Devonian) 
of Widder, Ontario. Adherent to Spirifera mueronata, Conrad, and 
Cyrtina hamiltonensis, Hall. 
The following are peculiarly British Carboniferous species : 
Ascodictyon radians, Nich. and Eth., jun. 
1877. Ann. Mag. Nat. Hist., Ser. 4., vol. xix., p. 465, pi. 19, 
figs. 9-11. 
As described and figured by the authors this species can only 
be accepted as a very doubtful ally of some of the fossil species of 
Ctenostomatous Polyzoa. Figures 9 to 11 are most perfect in their 
delineation and the description is exact ; but there is one feature in 
fig. 10 so unlike any fossil belonging to this group that I have 
heretofore examined, which makes me hesitate to accept it. That is 
the central pit-like cavity which is well shown in the figure. It seems 
to me that this is the basal part of some, at present unknown, Car- 
boniferous Polyzoa, possibly allied to the Ctenostomatous group. My 
own examples show exactly the same characters depicted by the 
authors, but it lacks the connecting hollow stoloniferous filamentous 
threads so frequently referred to in the descriptions of Ascodictyon 
and Vinella species in this paper. 
Ascodictyon Youngi, sp. n., pi. IV., figs. 3 and 4. 
Zoarium composed of pyriform vesicles occasionally disposed in 
stellate cluster, similar to other species already described. These 
vesicles are connected together by filamentous, hollow, unornamented 
threads, which creeps along and undulate with the irregularities of 
the surfaces to which the forms are attached. The type species is 
