HA RD WICKE'S SCIENCE- G OSSIP. 



275 



different specific names, there is a tendency of some 

 to ally with Silurian, while others approach Carboni- 

 ferous species in character. But every fragment given 

 by Nicholson is well described — a property that adds 

 much to the value of his specimens. One of these, 

 Fenestella magnified, bears a close resemblance in its 

 non-poriferous aspect to F. laxa of Phillips. To this 

 particular point Nicholson himself draws the attention 

 of the reader. I do not, however, set a very high 

 value upon Phillips' F. laxa from the Carboniferous 

 or Devonian series. It is very loosely described, and 

 very loosely figured, both in his Palceozoic Fossils, 

 and in his Geology of Yorkshire. Nicholson's species, 

 then, has this advantage over the older description ; 

 it is well figured and well described. The poriferous 

 aspect is unknown. He says : " I have only seen a 

 single specimen of F. magnifiea, and that only exhibits 

 the reverse side of the ccenecium, but the general 

 character of the frond so distinctive, that I have no 

 hesitation in founding a distinct species for its recep- 

 tion. It is from the Carboniferous Limestone of Port 

 Colborne, Canada."* 



F. marginalis (Nich.) is a very peculiar species. 

 It is described from a mere fragment, but the charac- 

 ter is distinct. The polyzoary was fan-shaped, but 

 of unknown dimensions.! In his critical remarks, 

 Nicholson says : "The specimen does not enable me 

 to affirm with certainty that the two marginal rows 

 of cells were separated by a medium keel, but it 

 appears highly probable that this was the case. In 

 the genus, or sub-genus, Fenestrellina (D'Orbigny), 

 the mesial keel, separating the two rows of large 

 lateral cells, carries a central row of minute cells. In 

 F. marginalis, however, the space between the lateral 

 rows of cells carries a series of minute crowded cells, 

 which are arranged in two, or sometimes in three, 

 alternating rows ; so that the central keel, if present, 

 must have exhibited the openings of two or three 

 rows of cells. This character, so far as I am 

 aware, has not hitherto been noticed in any species 

 of Fenestella, except F. rigidnla (M'Coy), and it 

 may, perhaps, afford a ground of sub-generic dis- 

 tinction. "J 



Fenestella filiformis (Nicholson) is the most 

 beautiful and delicate Fenestella that I have ever 

 seen. It is finer in the branches than the finest and 

 most delicate of any of my Carboniferous species. 

 The specimens are only in fragments, and the celluli- 

 ferous aspect is unknown. Of the branches, Nicholson 

 says, fifteen or sixteen of these occupy the space of 

 a quarter of an inch. 



Another species from the Hamilton group of the 

 Devonians of America is figured and described by 



Nicholson, which he dedicates to his friend David- 

 son. It is the Fenestella Davidsoni. From the 

 peculiar growth of the frond, it approaches nearest in 

 character to the F. Milkri, of Lonsdale, but both the 

 branches, fenestrules, and number and character of 

 cells are altogether different from that species. " In 

 the general aspect of the celluliferous surface and the 

 sinuous course of the branches, the species makes a 

 close approach to some of the species of the genus 

 Retepora ; but the presence of non-poriferous dissepi- 

 ments, and the existence of a keel separating two 

 rows of cells, seem to justify its reference to the genus 

 Fenestella."* In his "Ontario," Nicholson gives 

 another species, F. nervata, but having no access to 

 his work, I am unable to describe it. 



There is a striking peculiarity, however, about the 

 Silurian and the Devonian Fenestella when com- 

 pared with the Carboniferous species, which marks 

 them as distinct. But there are no arbitrary lines 

 about any of the Palaeozoic group, except in the F. 

 rigidnla and F. marginalis. If the poriferous 

 character of the keel, or the place the keel should 

 occupy, has not been exaggerated, this is peculiar ; 

 but, as I have been myself very much deceived in the 

 apparently poriferous keel,f I merely record my 

 doubt, with all due respect to the describers of these 

 species. Some specimens, too, show this poriferous 

 keel ozitwardly, but when reduced to sections, the 

 real cells are contiguous, and all the keel that exists is 

 the thin, wavy line which separates the two rows of 

 cells, and even this apparent line is nothing more 

 than the impingement of the walls of the separate 

 cells one upon the other. 



The Fenestella group seems to have reached its 

 climax in the Carboniferous seas. No fewer than 

 twenty-two species have been described by Phillips, 

 M'Coy, and others, to which Mr. Robert Etheridge, 

 jun., has added two others from the Scottish series 

 of Carboniferous shales. Many of these species are 

 fictitious ; the characters of some of them have been 

 described from fragments of other species. As, how- 

 ever, my friend G. W. Shrubsole, F.G.S., is engaged 

 on a complete revision of the Carboniferous Fenestella, 

 I will just here indicate the specific character of a 

 few only of the list. F. membranace, Phillips, is a well- 

 marked and characteristic species. It is elongate and 

 conical, bearing— generally — three small pores on each 

 side of the fenestrule ; it has, moreover, long, solid 

 non -poriferous roots. F. antiqua, Lonsdale, Retepora 

 antiqua, Goldfuss, and F. snb-antiqzia, D'Orb., 

 are included with this species as synonyms. 

 F. flabellata, Phillips, vary very much in different 



* Geo. Mag., May, 1874, p. 197. 



t As the descriptions of these species are easily accessible to 

 the geological student, I do no more than draw his attention 

 to a few of the minute details of Nicholson— reference to the 

 larger description will well repay him for the trouble. 



% Prof. H. H. Nicholson. New Devonian Fossils, Gso. 

 Mag., May, 1874. 



* Geo. Mag., 1875. 



t " I believe that all that has been written about poriferous 

 keels on the Fenestella is wrong, and that these so-called pores 

 are only worn-down rows of tubercules. Like you, I have 

 sectioned specimens showing these worn tubercules, and find 

 they lead to nothing, and have no connection with the cells. — 

 Mr. John Young, F.G.S. 



