Geological Society. 235 



baseof pelvlcs. Caudal ernarginate. Caudal peduncle 2 1 as 

 long- as deep. A rather broad dark longitudinal band along 

 the middle of the side, ending at the base of tlie caudal ; 

 vertical fins barred with 3 to 5 series of dark spots. 



A single specimen, 55 mm. in total length, from the La 

 Plata. 



Allied to 0. affinis, Steind., whicli has a median ridge on 

 the supraoccipifal and the fins unspotted, and to 0. vitlatus, 

 Regan, whicli has the supraoccipital less elevated, the scutes 

 fewer, and the coloration somewhat different. 



3. Po&cHia heterist'ia. 



Depth of body about 3i iu the length, length of head 

 nearly 4. Snout shorter than eye, the diameter of which is 

 3 in the length of head ; interorbital width more than ^ the 

 length of Lead. 27 or 2% scales in a longitudinal series. 

 Dorsal 6-7 ; origin equidistant from end of snout and middle 

 (.c? ) or posterior part (?) of caudal fin ; last two rays, in 

 the male, produced into long filaments. Anal 8; origin in 

 advance of that of the dorsal ; fin pointed (?) or modified 

 into an introniittent organ whicli is a little shorter than the 

 head ( (;J ). Pectoral a little shorter than the head; pelvic 

 fins longer in the male than in the female. Caudal rounded. 

 Olivaceous ; edges of scales darker ; some blackish vertical 

 streaks on tli« side ; a vertically expanded blackish spot at 

 the base of the caudal fin ; male with a short blackish stripe 

 near the upper edge of the caudal fin. 



Two specimens, 35 mm. in total length, from Para. 



PROCEEDINGS OF LEARNED SOCIETIES. 



GEOLOGICAL SOCIETY. 



December 16th, 1908.— Prof. W. J. Sollas, LL.D., Se.D., F.Pt.S., 

 President, in the Chair. 



The following communication was read; — 



* On the Igneous and Associated Sedimentary Ptocks of the 

 Tourmakeady District (County Mayo).' By Charles Irving 

 Gardiner, M.A., P.G.S., and Prof. Sidney Hugh Reynolds, M.A., 

 F.G.S. With a Paheontologieal Appendix by Frederick Richard 

 Cowper Reed, M.xl,, F.G.S. 



The general succession of the Ordovician Rocks of the district 

 appears to be as follows : — 



