2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



preserved small echinoids. The brachiopods are fairly well silicified. 

 The silicification is not coarse or crude in the large specimens, but it is 

 in some of the immature ones. In general the specimens are brittle 

 and fragile and must be handled with great care. 



These brachiopods occur in the Mural limestone but, because of the 

 isolated character of the hill, the exact stratigraphic position of the 

 specimens is uncertain. Ransome, who defined the Mural, states that 

 "The little hills near the eastern edge of the quadrangle north of Hay- 

 Flat are composed mainly of the hard limestones of the upper member 

 of the formation. Some of the beds here contain abundant corals 

 (Astrocenia and another form not collected). Caprina, and a number 

 of little brachiopods (Rhynchonella, TerebrateUa and Terebratula) 

 not seen at any other locality in the quadrangle." 



Stoyanow (1949, p. 20) divides the Mural limestone into three 

 units: (a) Basal thinner-bedded limestone with Orbitolina texana; 

 (b) massive "rudistid" limestone, and (c) thinner-bedded limestone 

 with Orbitolina texana. He says: "In the basal beds of the Mural 

 limestone, small brachiopods, corals, specimens of Lima miiralensis, 

 and large forms of Lunatia? sp. often occur. The massive limestone 

 is usually replete with Radiolites? sp., whereas the specimens of 

 Caprina sp. are comparatively rare and come from the thinner-bedded 

 layers below the reef." These remarks suggest that Stoyanow identi- 

 fied the brachiopod beds as low in the Mural. Perhaps brachiopods 

 occur in more than one level and were not seen by Ransome. At any 

 rate the Mural limestone is now placed (Cobban and Reeside, 1952) 

 at about the middle of the Albian stage in the Lower Cretaceous. 



CRANISCUS HESPERIUS Cooper, new species 

 Plate 3 A, figures 1-3 



Pedicle valve unknown. 



Brachial valve a low cone about medium size for the genus, sub- 

 rectangular in outline ; length about two-thirds the width ; maximum 

 width in anterior third; sides slightly oblique and gently rounded; 

 anterior margin broadly rounded; anterolateral extremities narrowly 

 rounded ; posterior margin nearly straight. Apex approximately 

 central, blunt ; anterior slope steep ; lateral slopes about as steep as an- 

 terior slope, but posterior slope gentle. Surface irregular. 



Interior with low median ridge rising to a sharp point at the valve 

 middle; anterior adductor scars narrowly elliptical, obliquely placed 

 and forming low ridges which, with the median ridge, divide the valve 

 into three parts ; posterior adductor scars large, but lightly impressed. 

 Anterior half with strong pallial ridges. 



