167 



cific name of intermedia, is stated by him to be not uncommon in the 

 Frith of Forth. Length 2 feet ; body thin ; snout sharp and pro- 

 minent ; tail rather short, witli a row of spines placed on the me- 

 sial line only, not extending further up than to the base of the anal 

 fins. Body perfectly smooth on both sides; eyes rather small, with 

 a spine placed in front of each ; teeth small, not so sharp as in the 

 grey skate. Body above, dark olive-green ; on the under-surface 

 dark grey, with minute specks of a deeper colour. (See Plate II.) 



It is distinguished from /?. latis by the rose being longer ; the 

 first dorsal fin being more remote from the second, and the skin 

 on the back being perfectly smooth, which in the R. balis is covered 

 with small spicula and rough to the touch. 



It is at once removed from the R. Oxyrhynchus of Montagu, by 

 the under-surface of the body being of a dark grey-colour ; which 

 part in tlie R. Oxyrhynchus is perfectly white. 



Dr Parnell mentioned the names of 123 species of fishes found 

 in the Frith of Forth and neighbourhood, about 40 of which have 

 been added by himself from personal observation. Three of these 

 are new to Science and two new to Britain. 



3. Notice on the Composition of the Right Prismatic Ba- 

 ryto Calcite, the Bicalcareo-carbonate of Baryta of Dr 

 Thomson. By Professor Johnston, Durham. 



This mineral, as described by the author about two years ago in 

 the London and Edinburgh Philosophical Journal, presents a new 

 and very interesting example of the principle known to crystallo- 

 graphers by the name of dimorphistn ; having the same chemical 

 constitution as the well known Baryto Calcite of Brooke, but hav- 

 ing a form belonging to an entirely different system of crystalliza- 

 tion. In Dr Thomson's System of Mineralogy lately published, 

 however, it is described as a mineral species before unknown, hav- 

 ing a composition difi^erent from that of every known mineral, and 

 is therefore distinguished by the name of the Bicalcareo carbonate 

 of Baryta. 



To test his former analysis, the author re-examined the mineral 

 from the only two known localities : he analyzed also the Baryto 

 Calcite of Brooke, and the results are embodied in the following 

 Table :— 



