92 



SCIENCE-GOSSIP. 



erronea and Gorilla fiyae they form a semicircle, the 

 second fold being nearest the aperture. The shell 

 of Corilla odontophora is more regularly and less 

 coarsely ribbed than that of Corilla erronea, and 

 larger, although composed of only 4-4J whorls, 

 while the other two species have 5 whorls ; it 

 differs further from Corilla erronea in that the last 

 whorl is more deflected in front, more 

 tumid, and then suddenly contracted 

 behind the peristome, more resem- 

 bling Coyj/Za /rj^a^ in these respects, as 

 also in the presence of a quadrate 

 tooth on the basal margin of the 

 peristome. Before concluding the 

 consideration of this species, I would 

 draw attention to fig. loa, in which, 

 though the shell is adult, is seen 

 the immature form of palatal folds 

 immediately behind the callus of the mouth, and, 

 as already mentioned, a circumstance which shows 

 that the earlier folds are not invariably absorbed 

 on the completion of the shell. 



Corilla humherti, also Cingalese, is extremely rare 

 in collections. As Benson, in the paper cited above, 

 throws some doubt on the correctness of Dr. 

 Brot's figure of this species in the "Journal de 

 Conchyliologie," xii., 1864, t. 2, f. 6, I was pleased 

 to be able to give a nev,- figure of it, and I am in a 



position to confirm Benson's conjecture that the 

 original figure is slightly misleading, as the basal 

 palatal fold appears to be joined to the suture 

 owing to the position in which the specimen was 

 placed, but on tilting the shell from the left side 

 the fold is plainly seen to be unconnected with the 

 suture, and it is thus shown in my fig. 1 1 ; this fold 

 corresponds in position with No. 4 of 

 the other species, while the parietal 

 fold corresponds with No. 2 of the 

 others. The specimen having been 

 completely cut in half through the 

 median plane, a close examination 

 of the parietal fold reveals a slight 

 fracture, and the inference forces 

 itself upon my mind that, probably, 

 in the process of cutting, it was 

 partly cut away, and that it reached 

 further back than it now appears. This form 

 differs from the species already considered in 

 ha\-ing only one palatal and one parietal fold ; 

 it is also decidedly more rounded in outline, but 

 like Corilla odontophora and Corilla fryae, it has a 

 quadrate, but less elongate, tooth on the basal 

 margin of the peristome. 



The other species of Corilla will be considered in 

 a future communication. 



(To be continued.) 



II. — Corilla hi'.mberii 



MANGANESE ORES IN NORTH WALES. 



By N. E. McIntire. 



T N the v,-estern part of Merioneth, the district of 

 Ardudwy, beds of dialogite and peroxide of 

 manganese have been occasionally worked during 

 the last ten years. There are two interesting 

 features about these deposits, viz. : the occurrence 

 (comparatively rare, if we except the coal measures) 

 of a strictly comtemporaneous interbedded mineral 

 seam, and the chemical changes which have taken 

 place along the outcrop and to a certain extent 

 along the upper and lower bounding planes of the 

 stratum. 



Attention was shortly drawn to these facts by 

 Mr. J. G. Goodchild in a paper on " Mineral 

 Veins," read before the Geologists' Association in 

 1888, and in the" Geological Magazine " for January, 

 1887, there is an abstract of another paper on the 

 subject, presented to the British Association by 

 Dr. C. Le Neve Foster. Sioce these appeared, 

 several openings have been made for mining 

 purposes, and a few notes may be interesting. 



The district of Ardudwy is covered with 

 Cambrian rocks, known as the Harlech grits 

 and Barmouth sandstones, which consist of a 

 great thickness of conglomerates, grits and slaty 



beds, the last being of most frequent occurrence 

 in the upper part of the series ; their general dip 

 is easterly, but the strata have been thrown into 

 great polls with usually a north to south axis. 

 The hills of Diphws, Llethr and the Rhinogs, from 

 2,000 to 2,500 feet high, are composed of these rocks, 

 which stretch eastward to the gold-bearing beds 

 of the Tingula flags on the Mawddach. It is 

 probable, though not proved, that most of the 

 workings are along different outcrops of the same 

 seam ; but the ore is certainly found on other 

 horizons, and a manganese staining of the beds is 

 fairly common. It is chiefly in the valley of the 

 little river Artro and its tributaries which drain 

 the west slope of the Rhinog range that the mines 

 have been worked The outcrops range, as might 

 be expected, from the dip, in a north and south line. 

 In many places merely shallow trenches have been 

 opened along the outcrop, and in the distance the 

 excavations look like the course of a small railway 

 traversing the hill-sides. One outcrop has been 

 worked in an almost straight line for two miles 

 north from the new church at Barmouth. In 

 ascending Nant Col from the village of Llanbedr, 



