1 ( )( ) Hi 1 1 — Th e In verte hrate Fom h of t h c 



I have observed only a few specimens. Tliese occur witli 

 great scarcity in the Caprina limestone, in association with 

 Radiolites davidsoni at Belton and near Austin. The species is 

 named in honor of Mr. T. V. Munson, of Denison, Texas. 



This species resembles in general form the excellent figures of 

 0. JoanK Choffat, from the Cretaceous of Portugal. 



Radiolites davidsoni sp. nov. 

 Plate XIII. 



Description of Figured Specimen. — Very elongate, measuring over 

 40 centimeters ; slightly flaring at larger end and gently tapering 

 to small extremity ; somewhat sinuous, pointed, and attached 

 at lower end; exterior surface strongly marked by longitudinal 

 ribs and grooves, as follows : Two especially broad and conspic- 

 uous grooves extending the entire length of the shell on oppo- 

 site side to that sliown in large figure, but seen in small segment 

 and end view. These are accompanied liy two large corre- 

 sponding oblate ribs and a sharji, angular carina. These two 

 grooves, ribs, and carina occupy one of the sides of the sub- 

 triangular circumference. The carina is very prominent and 

 sharp, and extends from the smaller end to within about ten 

 centimeters of the large extremity, where it becomes exfoliated 

 and deflected like a mantle over and across the large ribs and 

 grooves. This carina forms the upper margin of the large 

 figure, and the angles seen in the cross-sections, and is opposite 

 the smaller angle of the semi-lunate interior. It is bordered 

 upon one side l)y one of the major grooves above descrilied 

 and upon, the other l>_y the somewhat flattened face shown in 

 the figure of larger cross-section, on Plate XIII. The remaining 

 two-thirds of the surface of the shell is marked by about fifteen 

 small linear ribs, separated by wide., slightly concave depres- 

 sions. Interior of shell a hollow cavity subpyriform or semilu- 

 nate in cross-section, and marked by a few widely separated 

 concave ])artitions occurring at intervals of three to five centi- 

 meters. ()|)])osite the left hand major groove there is a slight 

 })rojeciion ext(;nding the length of the interior whicli makes a 

 narrow sinus in the casts wlien found. Tlie interior is usually 

 filled with calcite crystals. 



Shell, irregularly thick, varying from three-quarters to one- 

 h;vlf centimeter in different ])arts of the circumference. Outer 

 surface is very smooth between the flutings and marked by fine 



