No. 2.] WHITE OX CARBONIFEROUS AXD CRETACEOUS FOSSILS. 215 



except that they are more slender, their sides having a breadth of 

 from 2 to 2i millimeters, instead of from 3 to 5 millimeters, as in the 

 type-specimens ; but this is not thonght to indicate even a varietal 

 difference. The details being the same, the original description is 

 repeated here with only slight change. 



Corallum ramose, the branches comparatively few and not varying 

 materially in size from the main stipe ; transverse section triangular ; 

 all three sides poriferous ; the edges moderately sharp and sometimes a 

 little irregular ; the laminar axis consisting of three divisions, which end 

 respectively at the three edges and meet at the center of the corallum ; 

 pores well developed, but not arranged in the regular order that is com- 

 mon in this genus, nor are they bounded by any longitudinal or trans- 

 verse lines or ridges. Their mouths are moderately prominent, slightly 

 oval, the direction of the longer diameter of each being subject to no 

 regularity. 



This species differs from typical forms of Ftilodyctia in having three 

 flat or concave sides, instead of two convex ones ; in the axis being con- 

 sequently tripartite; and in the irregular disposition of the pores upon 

 the surface. 



BEACHIOPODA. 



Genus Eetzia King. 



Retzia ■woosteri (sp. nor.). 



Shell of medium size, moderately gibbous, both valves being nearly 

 equally convex ; hinge short; ears scarcely prominent; ventral valve 

 having a moderately broad, very shallow sums, which is scarcely ap- 

 parent at and near the umboual region and produces merely a broad 

 sinuosity in the front margin ; longitudinal convexity of the valve reg- 

 ular, but greater between the middle and umbo than elsewhere ; umbo 

 prominent and arched. Dorsal vah'e considerably shorter than the ven- 

 tral, regularly convex, showing only a slight if any elevation corre- 

 sponding with the shallow sinus of the ventral valve. Surface marked 

 by about 28 simx)le plications upon each valve, which extend from beak 

 to base, being separated by grooves of about equal width with the pli- 

 cations. Six or seven of these plications occupy the shallow sinus of 

 the ventral valve, and they occupy the whole surface except a small 

 plain space on each side of the umbo of the ventral valve, and a still 

 smaller adjacent space on each side of the umbo of the dorsal valve. 



Length from ventral umbo to front margin, 20 millimeters ; greatest 

 width, which is in front of the middle, 18 millimeters; greatest thick- 

 ness, both valves together, lOi- millimeters. 



In general form and character of surface-markings this species is re- 

 lated to B. -iftoMarcou {^:=R.pnnctH[fera Shumard) ; but, besides being a 

 much larger and comparatively a less gibbous species, it bears nearly or 

 quite double the number of plications upon each valve that is borne by 

 B. uta. 



