368 Brigadier Silvertop^s Sketch of the Tertiary Formation 



ceous ingredient forming the lower part of the deposit at the latter 

 town, and the upper or superior portion at Alaurin. Dentalia, 

 Triton nodiferum^ Ostrea, and Natica, are found at each loca- 

 lity. ThePecten pleurenectes, so abundant at Malaga, I did 

 not find at Alaurin, nor the Venus, which abounds in the de- , 

 posit at Alaurin, in that at Malaga ; nor in the latter any shark's 

 teeth, or vertebral remains of delphinus. Before I conclude the 

 description of this lower group, I think it necessary to allude to 

 the difference in level between the beds at Malaga and Alaurin 

 el Grande. At the former locality, the strata are not more than 

 50 feet above the level of the Mediterranean, while at the latter 

 they are at the height of 900 or 1000 feet. This difference of 

 level, I conceive, is connected with the highly crystalline charac- 

 ter of the limestone of the ridge on which the tertiary beds 

 rest, and the subjacent mass of serpentine which occurs at the 

 N. N. W. end of the ridge, or Sierra de Mijas. 



^d'&r'SttpeHdt Group (see Sect. 1. and 3. PI. II.)— In the 

 higher and undulating part of the little tract first alluded to 

 contiguous to Malaga, there are several low eminences {% 2. 2. 

 in sect. 1), where the horizontal bed of sandy loam and marl, 

 and the masses of conglomerate that belong to this group, 

 are well seen. The immense size of the ostreae found in these 

 beds is worthy of attention (Ostrea crassissima ? of Lamarck), 

 and particularly when compared with the small ones met with 

 in the subjacent or lower part of the tertiary deposit. The 

 predominating shells, however, are pectens of various undescrib- 

 ed species, but very similar to those now found along the Medi- 

 terranean shore. The balanus is also frequently found in these 

 beds. As the argillaceous deposit of the group 1 A is at a consi- 

 derably lower level than these beds, and as it is seen forming the 

 left^bank of the Guadamedina Rio that bounds this tract towards 

 the wfest, I presume that it extends under the beds of the second 

 group, and has once filled up the whole of the area under con- 

 sideration. The section 3. (PI. II.) of ground on the opposite or 

 western side of the Rio Guadamedina will also, I believe, prove 

 its subposition, although I have never seen an instance where the 

 beds of group 2. overlie the deposit or group 1 . Each group, how- 



