The Lower Pliocene Bone-bed of Concud, Spain. 205 



about 3,000 feet above the level of the sea, and capped with irregular 

 thin beds of limestone. They are so barren as to be scarcely of use 

 even for the pasturage of sheep, of which poor flocks are kept. At 

 the time of our visit the red-legged partridge was in season and 

 very abundant. 



For a distance of about four miles along the outcrop we continually 

 found traces of bones and teeth in the talus from the softer beds 

 immediately beneath the limestones ; but the bone-bed itself was 

 best exposed in the vertical walls of the classical ravine — the Barranca 

 de las Calaveras, or Valley of Skulls — originally described by 

 Torrubia and Bowles. We eventually baited here and spent a few 

 days in extricating the fossils. 



The northern wall at the entrance of this small ravine is shown 

 in the photograph reproduced in Plate XII. At the top (A.) are 

 observed the overhanging ledges of limestone. Beneath these is 

 a layer of comparatively soft marl and sand (B) which is filled at most 

 spots with bones. The lower half of the section then consists of hard 

 red marl and sandy layers (C), with occasional beds of well-rounded 

 pebbles, which form prominent ridges on the weathered face. At 

 this point the bone-bed is inconveniently situated for satisfactory 

 excavation. We therefore followed it to the head of the ravine, 

 where the floor rises to its level and makes it comparatively accessible. 



At the point where our chief excavation was made, the over- 

 hanging beds of limestone are from 4 to 6 metres in thickness. 

 They form irregular layers, some consisting chiefly of the fresh-water 

 shells described by Vilanova, others composed entirely of chemically 

 precipitated travertine. The shelly layers contain an occasional 

 bone or tooth, but no accumulation of mammalian remains. At the 

 base of the limestone there are traces of lignite and bituminous 

 marl, also enclosing a few scattered bones and teeth. Next below 

 is a bed of white marl, about one metre in thickness, almost un- 

 fossiliferous but with occasional traces of lignite. Then follows 

 a greenish-yellow, soft, sandy bed, about 30 centimetres thick, with 

 an admixture of white and greenish marl, sometimes bituminous 

 at the base. This is the true bone-bed, and immediately below it 

 occurs the unfossiliferous series of brick-red sandy marls and con- 

 glomerates so well shown in Plate XII (C). 



The bones in the bone-bed do not form an absolutely continuous 

 mass, but occur rather in dense patches. They vary in state of 

 preservation, and at the spot where we worked they were made 

 fragile by moisture and much distorted by crushing. The specimens 

 we obtained, indeed, suggest that they had become more or less 

 rotten even before burial ; and I observed no satisfactory evidence 

 of naturally associated bones — either pieces of limbs or of vertebral 

 column — such as are common in the bone-beds of Pikermi. The 

 teeth alone proved to be well preserved, and complete jaws were 

 often met with. There were no associated pebbles. 



The large majority of the remains in the Concud bone-bed belong 

 to Hipparion gracilis. The teeth of this species are especially 

 common everywhere. There is also evidence of a larger variety 



