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DIASTOPORA. 
layer.’ He restricted this structure to Mesenteripora, and doubtfully 
removed that genus to the family of the Entalophoridac. 
In referring to M. Pergens’ treatment of this genus in the Cat. 
Jur. Biy.^ the remark was made that “ Pergens has retained the 
genus \_Diastopora\ for the unilaminate forms, transfenlng Bidias- 
topora and Mesenteripora to the Entalophoridae.” This remark has 
been severely criticized by M. Canu,^ and it may be based on a 
misunderstanding of M. Pergens’ treatment of one species. 
Pergens refers to Diastopora twelve ‘ species ’ ; of these eight 
‘ species ’ are Berenicece, and are therefore necessarily unilaminar ; 
of the erect species J). tahulosa, B. mutata, and D. escharoides 
are admittedly unilaminar ; while all the species included in 
Mesenteripora are stated, according to the diagnosis of that genus, 
to have “zoecies sur les deux faces.” The only species at all 
doubtful is B. marginata^ in respect of which Pergens ^ says : 
“ la colonie n’a pas de lame germinale, mais elle estformee dedeux 
couches adossees, comme on les rencontre dans les Biastopora du 
Bathonien.” It seemed to me that H. Pergens thus implied that 
B. marginata consists of two unilaminar fronds, growing back to 
hack by some accident of growth, and that the bilaminar arrange- 
ment of his species of Mesenteripora is essentially distinct. It 
would possibly have been better to say that Biastopora is simply 
laminar instead of unilaminar, which might have prevented 
M. Canu’s misconception of my intei’pretation of M. Pergens’ 
reasons for removing Mesenteripora marginata to Biastopora, 
The ‘ Germinal Later.’ 
Reference to this question necessitates consideration of the taxo- 
nomic value of this ‘ lame germinale.’ The term is inappropriate, 
as the layer has no proved connection with any germinal function, 
and accordingly in the Cat. Jur. Pry. (p. 13) the merely descriptive 
name of ‘ zoarial lamina ’ was adopted for it. Such a layer occurs 
most strongly developed in bilaminar erect zoaria, and especially in 
those with crowded zooecia ; hut a similar layer forms the reverse 
face of unilaminar fronds, and forms the base of Berenicean colonies 
(round the margin of which it often projects). D’Orbigny called 
^ Cat. Jur. Bry. p. 117. 
* Canu. Ovic. Bry. Ocg. : Bull. Soc. geol. Fr. ser. 3, vol. xxvi. p. 265. 
® Pergens : Bevision, p. 336. 
