108 ]!tIE. J. E0itA2s"ES OK THE [Feb. I9I2, 



quarry. In the upper quarry and at Tres Eios, however, the rock 

 is seen to be largely composed of cirripede-remains. These agree 

 with Balanus, both in external form and in the characteristic 

 complex structure of the shell, as shown by a thin transverse 

 section (see PI. IX, fig. 1). In some specimens they are so crowded 

 together that they have been forced to assume a polygonal outline ; 

 and, where they have been broken across by joints and weathered, 

 the appearance almost suggests a very large compound coral 

 possessing no internal structure. 



The microscope also reveals numerous badly-preserved forami- 

 nifera, which in general form suggest Orbitoides, as also a few 

 indeterminable corals. Mr. R. T. Hill records that, by polishing the 

 limestone, it is seen to consist largely of Inoceramus and Rudistes, 

 and therefore he calls it Cretaceous. A.n examination of a large 

 number of specimens entirely fails to confirm this statement : the 

 only structures that might suggest Inoceramus being the cross- 

 sections of Pecten. 



The occurrence of such vast numbers of Balani makes it ex- 

 tremely improbable that the rock could be pre-Tertiary, while a 

 Tertiary age would be more in accordance with the idea of con- 

 temporaneous volcanic action to which reference was made above. 



(ii) Marls and sandstones. — In his work on Central America, 

 Dr. Sapper^ mentions a sandstone apparently underlying the San 

 Miguel Limestone, and records the impression of a Pecten in it ; 

 but this appears to be almost the only reference to sediments other 

 than limestone in this area. I have been able to discover several 

 different localities in which marls or sandstones are exposed ; from 

 two of these fossils have been obtained. As a general rule, there 

 appears to be a belt of argillaceous and arenaceous rocks lying 

 between the San Miguel Limestone and the level floor of the valley. 

 The cart-track from the village of Patara to the limestone quarries 

 passes over this belt, and several good roadside exposures are seen. 

 The deposits here vary from a loose friable sandstone often stained 

 bright red, to a very fine-grained pale-yellow marl, this latter 

 being in places fairly fossiliferous. In all the exposures seen 

 these rocks have been so affected by irregular jointing, that the}' are 

 reduced to quite small angular fragments : this, together with a 

 certain amount of staining by infiltration, has entirely obliterated 

 the bedding, so that no definite clue can be obtained to the probable 

 relation between these beds and the San Miguel Limestone, although 

 it is more probable that they underlie than that they overlie the 

 limestone. 



The marl contains an assemblage of fossils entirely difterent 

 from those of the limestone ; there is a much more varied fauna, 

 but, unfortunately, the fossils are very fragmentary and badly 

 jireserved : the genera Ptctuncidus, Astarte, Area, and Pyrida are 

 represented. 



1 PeteniK Mittli. Erganzungsb. xxxii (1906) Xo. 151, p. 29. 



