EXPLANATION OF THE PLATES AND WOOD-CUTS. 



Plate XLVI. 



Map and Sections. 



The Map is intended only to assist the reader in following the description con- 

 tained in the paper, and to exhibit a general view of the distribution of the rocks 

 occun-ing between the Taptee and Pennar rivers. However imperfect this slight 

 sketch confessedly is, it is hoped, that by embracing almost all the information yet 

 obtained respecting this extensive region, it will correct the erroneous opinion en- 

 tertained by many, of the simplicity of the geological structure of the South of 

 India, and afford a nucleus around which additional and connected observations 

 may be gradually arranged. 



It has been found impossible to employ more than two colours for granite, 

 gneiss and mica, chlorite and hornblende schists ; for although many good obser- 

 vations have been made on the distribution of these rocks in certain parts of the 

 country, yet the boundaries have not, in general, been clearly distinguished, nor is 

 it always easy to do so. Where the stratified primary rocks prevail more abun- 

 dantly than granite, a purple tint has been employed. 



The Diamond sandstone and argillaceous limestone appear to constitute parts 

 of one formation, and it has therefore been thought better not to distinguish them 

 in a map of such small dimensions ; though an attempt to do so has been made 

 in the sections. The laterite is introduced only where it occurs resting on basalt, 

 at Beeder in the Deccan ; its limits are unknown. Near Nellone, a nearly 

 similar formation rests on the primary rocks, and is probably formed from their 

 decomposition in situ. 



The trap is represented the same colour as in illustrations to Col. Sykes's 

 Memoir on the Deccan, (Vol. iv. PI. XXVI.) to enable the reader to connect the 

 district represented in Col. Sykes's map with that contained in the accompa- 

 nying map. 



The section, fig. 1, at the top of the plate, extends from Bundlecund, beyond 

 the north boundary of the map, to the Bangnapilly diamond-mines, situated be- 

 tween the 15th and 16th degrees of north latitude. 



Section, fig. 2, extends across the Peninsula from the coast near Atchera (lat. 

 about 16°) to Madras. 



Plate XLVII. 



Organic remains collected by Mr. Malcolmson,and described and engraved by Mr. James 

 de Carle Sowerby : p. 5.50. 



Fig. 1. Chara Malcolmsonii. Oblong, spheroidal, with 10 ribs; three of the ribs are 

 produced at the apex. Natural size and magnified. 



This capsule is composed of 5 tubes, each of which is curled twice round. The 

 figures represent a cast of the interior, the tubes being split down, and the outer 

 halves broken away and left in the chert. The specimens are silicified and consti- 

 tute almost the entire mass of the rock, in which they occur associated with 

 PhyscE and Paludina. 



