CORRESPONDENCE. 



185 



Mr. Davies, in his communication in your April number, refers to the 

 greater imbrication of the scales " mentioned by Mr. Mitchell " (no new 

 discovery), and also to the general character of the ridges on the scales, as 

 being differently and distinctly marked in the two genera. Undoubtedly, 

 retaining the old nomenclature, the scales in II. giganteus, H. nobilissimus, 

 etc., are less imbricated, and have the ridges more wavy and boldly marked 

 than in II. Flemingi, but on examining a large collection of the Dura Den 

 fishes, a pretty regular gradation from the less to the more imbricated 

 and from the bold wavy ridges of the larger species to the almost parallel 

 and delicately marked lines found on the scales of some of the others, may 

 be traced. Mr. Davies's remark as to the position of the scales showing 

 the crescent of points scarcely corresponds with my experience, but this 

 may very probably be occasioned by our observations being principally 

 confined to different species. In H. Flemingi many scales on every part 

 of the body sufficiently preserved and exposed, which I have yet examined, 

 show the crescent of points, while in other species these are only to be 

 found on the scales along the flanks. 



I am very glad to learn from Mr. Davies that the characteristic speci- 

 men of Holoptychius Andersoni in the British Museum shows, what I have 

 been unable to detect in that species, the crescent of points, — as this is a 

 considerable step towards clearing up the dispute Holoptychius v. Glyp- 

 tolepis. Professor Huxley states in his introductory Essay to the X De- 

 cade of Plates published in connection with the Geological Survey (p. 9), 



The clear recognition of the fact that this elegant structure really cha- 

 racterizes Glyptolepis is of great importance, for ... it enables one to dis- 

 criminate between Holoptychius (whose scales have no semilunar area of 

 backioardly- directed points) and Glyptolepis." 



I have to express my gratification at the notice Mr. Davies takes of these 

 communications ; to local geologists situated at a long distance from col- 

 lections affording facilities for comparing the many species of such genera, 

 and ever comparing nearly allied genera with one another, such hints as 

 he gives are very valuable indeed. I am, dear Sir, yours truly, 



James Poweie. 



Reswallie, April 10th, 1863. 



Bones at Macclesfield. 



Dear Sir, — You obligingly inserted a paper from me in Yol. IY. of the 

 ' Geologist,' and the following communication may perhaps interest some 

 of your readers : — 



A few days ago, in levelling a piece of ground as a site for an infirmary, 

 a few bones and a molar tooth w r ere discovered by the workmen. Thirty 

 feet below, there is a small brook, which runs into the river, distant about 

 a quarter of a mile, at a further decline of about 70 feet. The bones were 

 embedded a little apart from each other, in a layer of fine sand about 18 

 inches in thickness ; above that there was a deposit, about 2 yards in depth, 

 of coarse sand and gravel, thickly studded wit h large waterworn pebbles of 

 the Primary, with a few of the Secondary sandstone rocks. About IS 

 inches of soil (alluvium) surmounted the whole. The excavation was con- 

 tinued about 2 yards below the bed of sand in which the bones were found, 

 and it consisted of thin layers of gravel with marl and fine sand at irre- 

 gular intervals, interspersed with carbonaceous markings and thin scams 

 of drifted coal or shale. I have resided here many years, and the osseous 

 remains I have sent for your inspection are the first I have scon or hoard 

 of; and, with the object of affording assistance to a solution of this disco- 



VOL. VI. 2 B 



