on the Genus Paleacis. 223 
from the previously mentioned lobate character than any thing 
else, but still with a definite, although rough, kind of radiation. 
The frequent occurrence of this feature will therefore render 
the figure given* by Herr Ludwig of his Ptychochartocyathus 
laxus not quite so hypothetical as Prof. de Koninck ap- 
pears to considerft. Another peculiarity which occurs is 
the piling or growth of the cells one upon another. This is 
not of very frequent occurrence, and probably took place when 
the space for the growth of the colony was restricted (Pl. XII. 
fig. 17). One of the most characteristic points connected with 
P. cyclostoma is the broad base (Pl. XII. fig. 3) and concen- 
tric basal swellings, attachment taking place either by a large 
or small portion of the former. Usually the colony is fixed 
by the whole area of the base to some foreign body large 
enough for its entire expansion ; but, on the other hand, when 
adhering to an object of lesser dimensions than itself, a groove 
or concavity is formed in the base, and the free portion, which 
would otherwise, as in the first instance, have been also ad- 
hering is covered with concentric folds or swellings. We have 
observed P. cyclostoma attached to the following bodies :— 
Crinoid stems; various species of Zaphrentis; Huomphalus 
carbonarius, Sow.; Bellerophon Urii, Flem.; Dentalium ingens, 
De Kon. ; Productus longispinus, Sow. ; Productus punctatus, 
Martin ; Chonetes; and fragments of shelly matter in too un- 
satisfactory a condition to be determined. 
Under certain conditions the colony of P. cyclostoma ap- 
pears to have taken upon itself an irregularity of growth 
which, had the individuals so distinguished been found by 
themselves, would have gone a long way towards the esta- 
blishment of a new species (PI.XII. figs. 18-20) ; but between 
the typical P. cyclostoma, with its expanded base and more 
or less depressed lobate form, on the one hand, and the variety 
with elongated and laterally spreading corallites on the other, 
there are so many gradations and intermediate forms, that we 
cannot see the justice of more than a mere varietal separation. 
Our eminent friend and colleague, Prof. L. G. de Koninck, 
has described and figured { such a form under the name 
of Paleacis compressa, Meek & Worthen ; but with the advan- 
tage derived from the examination of a large number of speci- 
mens, as previously stated, we feel convinced that the form 
figured by our friend is identical with the variety of P. cyclo- 
stoma now under discussion. Certainly we have not had an 
opportunity of examining the specimen upon which Prof. de 
* Paleeontographica, xiv. t. 69. figs. 2, 2a, 
+ Nouvelles Recherches, 1° pt. p. 160. 
t Ibid. p. 158, pl. 15. £. 7. 
