133 



From Lingulepis Gregwa it is easily distinguished by the short callus 

 of the dorsal valve, and by the sculpture. - 



LINGULEPIS LONGINERVIS, n. sp. PI. VII figs. 6, a g. 



A thickshelled specie*, with the dorsal somewhat, and the ventral valve Lingulepis 

 greatly prolonged. 



The ventral valve has an even arch to the anterior and posterior end 

 on the axial line ; it is more strongly arched down at the sides in the post- 

 erior half than elsewhere. The sides are straight from the umbo, beyond 

 the middle of the shell, and thence regularly rounded. Interior. This 

 shows a high hinge area, with very oblique strife on the areal borders, 

 and prolonged margin of the cardinal area, extending forward along the 

 edge of the valve; the pedicle groove is deep and broad ; the areal slopes 

 have a great width near the umbo, and increase slowly in going forward. 

 Extending from the hinge forward along the middle of the valve is along 

 visceral callus, on each side of which at the mid length of the valve are oval 

 scars (of the central muscles ?) ; in front of these and more approximated is 

 a small pair of scars ( " k " laterals ?) The print of the laterals in these 

 valves is heavy and extends nearly as far forward at the central scars ; 

 they are not as far from the central scars as these are from each other. 



The dorsal valve is oval and has a low flat umbo ; in most adult 

 valves the posterior slope is strongly arched down, and the lateral slopes 

 less so. The valve for most of its length is flattened along the median 

 line. Interior. The hinge area is high and as in the ventral, the striae 

 of the slopes are quite oblique. There is a well marked long visceral cal- 

 lus extend to within an eighth of the front of the valve. The paired 

 scars of the centrals are nearly two thirds of the length of the valve from 

 the umbo, and those of the " j '' laterals of adult valves less then one 

 quarter of the length of the valve from its front. The laterals " 1 " and 

 "k," are well shown in this valve, "1" being opposite the central muscles 

 and "k" more advanced, smaller, and oblique; the above laterals are 

 about as far from the centrals as these are apart. Traces of vascular 

 trunks are seen inside of the laterals. 



Sculpture. Beside the concentric growth grooves, which are prominent 

 on these valves, the lateral slopes display fine concentric ridges, about 

 ten in the space of a millimetre ; these little ridges are somewhat irregular 

 in their course, and sometimes anastomose ; elswhere they sink down 

 so as to become rows of granulations ; 011 the dorsal slope they merge into 

 an irregularly rugose surface, across which run broken, radiating ridges, 

 directed toward the front margin. 



