DUBLIN NATURAL niSTOET SOCIETT. 77 



bisson's kindness for dried specimens of eacli of those species from France, 

 and they appear to me to be quite identical with our own.''^ 



I now come briefly to contrast my new species with M. rotnta, and 

 M. denticulata; and, as in the instances of those two species, it will be 

 better first to point out where the new species agrees with them ; but 

 as that is, indeed, precisely in the characters in which they agree with 

 one another as detailed above, it will be, therefore, quite unnecessary 

 again to narrate those characters (vide supra). I say M. Thomasiana 

 agrees with all the common positive and negative characters of M. rotata 

 and M. denticidata given above; for the superficial apiculate projections 

 on the former cannot be called either papillae or granules, they are the 

 summits of the eminences disposed over the frond. The former seems 

 to me to have a greater affinity with If. denticulata than with M. ro- 

 tata, — indeed, in front view there is a liability of the former being con- 

 founded with it. I shall first draw attention to the distinctions between 

 them. 31. Thomasiana is notably smaller than M. denticulata (as it is 

 smaller than M. rotata) ; in the new species the basal and middle lobes 

 are mostly thrice dichotomous, in M. denticulata they are but twice di- 

 chotomous ; in the former, the ultimate subdivisions of the basal and 

 middle lobes when eight are bidentate, when four only, tridentate, — in 

 the latter they are four onl}^, and truncato-emarginate, with rounded, or 

 sometimes subacute, angles ; in the former, the terminal emargination 

 of the end lobe is rather deep and acute, — in the latter it is more shallow 

 and more ronnded. To compare 31. Thomasiana with 31. rotata, the 

 former is much smaller than the latter (which, indeed, is larger than 3f. 

 denticulata); in the former, the basal and middle lobes are mostlj^ thrice, 

 sometimes twice, dichotomous ; in the latter the basal lobes are con- 

 stantly twice, the middle lobes thrice, dichotomous ; in the former the 

 teeth of the ultimate subdivisions are not so lengthened as in the latter ; 

 in the former the middle lobe is narrow, and with nearly parallel sides 

 below, widening above, — in the latter the end lobe is more or less cam- 

 panulate ; in the former the end lobe is wholly included, its angles acute, 

 the central notch deep, acute — in the latter, the end lobe is slightly but 

 distinctly exserted, its angles somewhat produced and bidentate, its central 

 notch shallow and rounded. But, above all, the new species is I'emark- 

 ably distinct from loth 31. denticulata and 31. rotata, and indeed every 

 other species, by the striking projections at the base of the segments, 

 and by the superficial eminences. j^To distinctions can be draAvn ft-om 

 the sporangium in these species, as unfortunately it is unknown, that 

 of 31. denticulata excepted. It does not appear at all requisite to com- 

 pare 31. Thomasiana with any other species, as there is none other for 

 which there seems any chance of its being mistaken. Indeed, the only 



* Since this paper -was read I have had an opportunity, through the kindness of my 

 friend, Mr. W. Keay, of examining a gathering made near Dundee, in which M. denticulata 

 occurred, and in no point did his specimens differ from that species collected in this country; 

 and the same might be said of the other forms therein common to Scotland and Ireland. — 

 W. A. 



