82 NATURAL HISTORY SOCIETY OF DUBLIN. 



common specific name, M. Americana, M. Baileyi, M. ringens, and his 

 var. B. The second and third forms, M. Baileyi and M. ringens, seem 

 to be excluded from the immediate affinity at least of the first and 

 fourth, by the want of the curious additional obliquely disposed, more 

 or less nearly vertical processes, one springing from each of the front 

 surfaces of the terminal lobe, characteristic of the latter. Now, it seems 

 to be hardly admissible, in order to fit them in here, to presuppose the 

 existence of these processes merely from a certain amount of agreement 

 in general contour, and the more so, as they are neither alluded to nor 

 figured in their original descriptions by either Bailey or Ralfs.* If 

 these authors did not see them, then, it is to be presumed they did not 

 exist. Moreover, these two forms themselves seem to be distinguished 

 from each other by M. Baileyi being punctate all over, while M. rin- 

 gens is without puncta, and possesses a marginal series of granules border- 

 ing the sinuses. Irrespective of these characters, however, unless the 

 non-reconcileable intermediate forms be discovered, these two forms as 

 figured and described, if persistent, as Professor Bailey seems to convey, 

 appear to me to represent quite distinguishable species, not only from 

 the two other forms with which Dr. "Wallich has associated them, but 

 also from each other. In regard to M. Americana and Dr. "Wallich's 

 var. B, equivalent to M. Mahabuleshwarensis (Hobson), both of which 

 indeed agree in possessing on the end lobe the secondary processes 

 springing more or less obliquely as regards the plane of the frond, it yet 

 seems to me that here even more abundant differences inter se actually 

 exist. The former occurs in this neighbourhood (rarely, however), and 

 I feel pretty well acquainted with it, and I must own that I should 

 be beyond measure astonished to encounter the latter in our Dublin 

 pools ; but, even supposing that it did turn up, I should never, indeed, 

 for one moment imagine that I had met with but a variety of tbe known 

 British form. I venture to think they differ, indeed, as much as two 

 allied species need or can. To me, indeed, there appears a greater 

 affinity in character of surface between M. expansa, var. 7 ("Wallich), f 

 and the form in question, than between the latter and M. Americana 

 (Ehr.). In the two forms just pointed out the character of the margins 

 of the lobes is alike ; but the lateral lobes in Dr. "Wallich's " var. 7" are 

 not bipartite, and the end lobe wants the vertical processes. I have, 

 of course, never seen M. expansa, nor M. arcuata, nor " var. 7 ;" but I 

 feel bound to say, even though it be but conjecturally, that all three 

 seem to me to be abundantly distinct. 



In M. Americana the lateral lobes are short and broad, more or less 

 conspicuously divided in a dichotomous manner by both a primary and 

 secondary very shallow, simple incision, their sublobes short, expand- 

 ing, the ultimate subdivisions more or less acutely dentate ; in Dr. "Wal- 

 lich's var. B (if. Mahabuleshwarensis, Hobson), the lateral lobes are 



* Bailey, loc. cit., p. 37, PI. I., Fig. 11 ; and Ralfs, op. cit., p. 211, t. xxxv. Fig. 4. 

 f Loc. cit., PI. xiii., Fig. 9. 



