164 PERMIAN POSSILS. 



establishing of the genus Edmondia by De Koninck renders it necessary for me to 

 modify Allorisma by restricting it to the kind represented by Hiatella sulcata. Another 

 opportunity will herein occur to speak more in detail of the latter genus. 



There is much difficulty in distinguishing the various species of Edmondia, in con- 

 sequence of their resembling forms belonging to other genera, and rarely displaying the 

 essential characters of the genus. Thus the generic collocation of the so-called Sangui- 

 nolaria undata, Portlock, is far from being correctly determined. I am inclined to think, 

 if this species is not an Edmondia, that it belongs to a genus closely related to it ; as 

 there is some appearance of a deep vertical cartilage-plate (though much reduced in size, 

 compared with that of Edmondia sulcata, Ed. unioniformis, and other species), occupying 

 about one third of the length of the dorsal margin of the valves : perhaps it belongs 

 to the genus Orthonota of Conrad, which is typified by a similarly-formed shell, the 

 Orthonota undulata, Conrad, characteristic of the Hamilton group of rocks (Devonian) 

 in North America. 



Synonymous with Edmondia is Professor M'Coy's Sanguinolites^ which is typified 

 with Phillips's Sanguinolaria (?) angustata, a species having (as well as the one 

 [Sanguinolaria arcuata, Phillips] next in order of description in the ' Synopsis of the 

 Carboniferous Fossils of Ireland')^ all the characters of the present genus.^ 



Edmondia appears to be a singular genus, both in its cartilage fulcra and muscular 

 system. The former, as existing in Edmondia sulcata {Sanguinolaria id., Phillips), are 

 represented in t'late XX, figs. 2 a, 3, and 4. By referring to these figures, it will be 

 seen that the plates are situated within the umbonal cavity, and have a striking re- 

 semblance to a bivalve shell. The figures cited are copies of a fossil (cast) which was 

 originally in the state represented in figure 1 ; but by carefully chipping off the 

 umbones, it was made to display two plates, singly curving within each of the 

 umbonal cavities, as in figure 2 a : both occupy their exact relative position in (the 

 magnified) figure 4 ; and figure 3 is an enlarged representation of the most perfect one. 

 Having broken off the umbones of a number of specimens with the like result, I can 

 speak with confidence as to these plates belonging to the shell; and I am equally 

 confident, from what is displayed in several sections which I have made of the shell 

 from the dorsal to the ventral margin, that each one is attached by its upper margin 

 to the hinge-plate in both valves. Looking at such shells as Lutraria elliptica, we 

 discover that similar structures serve as supports or fulcra for the cartilage : we are 

 therefore led to conclude that the plates of the fossil under consideration have 



"^ Vide Synopsis of the Carboniferous Fossils of Ireland, p. 47. 



2 A specimen of Sanguinolarin (?) angustata in the Gilbertsonian collection of the British Museum, 

 exhibits the groove left by one of the cartilage fulcra : casts of Sanguinolaria arcuata, with the grooves left 

 by the cartilage fulcra, are rather common at Redesdale in Northumberland. 



^ Professor M'Coy has included species of various genera in his Sanguinolites : some appear to be 

 Allorismas (e. g., Sanguinolaria tumida, Phillips) ; and others Pleurophoruses {Sang, tricostata, Portlock) : 

 S. undatus is perhaps an Orthonota ; S. contortus appears to belong to an undescribed genus ; and ;S, 

 radiatus is seemingly a Janeia. 



