LOBIOA. 



I. 70LV03 Reeve, IM. 52, figs, 14-21. 



Shell oblong, strongly elevated, the dorsal ridge anirular, side- 

 slopes nearly straight. Surface Insterless, finely sculptured, variable 

 in color; sometimes hull' with chestnut streaks and darker angular 

 blotches on the central areas, fewer on the lateral areas ; sometimes 

 the lateral areas are olive-green, the dorsal region light, the sides of 

 the central areas brown or olive. The dorsal ridge is sometimes 

 staim (! with orange on each valve, and the same color often clouds 

 the sides also. 



The median valves are not beaked, even when young, but they are 

 falsely beaked or narrowly projecting at the sinus in front. Lateral 

 areas raised, sculptured with 8-12 low radiating cords bearing 

 rounded pustules, which are more or less entirely lost in adult spec- 

 imens. Central areas sculptured with numerous narrow raised 

 threads parallel to the dorsal ridge, their interstices wider than the 

 threads, and closely latticed across. Anterior valve strongly 

 elevated, curving forward at the summit, the anterior slope being con- 

 cave; sculptured with many radiating riblets which are pustulose 

 when not eroded. Posterior valve small, much depressed, with pos- 

 terior, terminal, elevated mucro ; posterior-lateral margins bounded 

 by an elevated rib ; posterior area extremely small, vertical, 

 perpendicularly ribbed, having a deep rounded excavation behind. 



Interior white ; tegmentum reflexed and sculptured along the pos- 

 terior margin of each valve; sutural-plates broad, separated by an 

 extremely small v-shaped sinus in the middle. Anterior valve hav- 

 ing 8, central 1 slit ; slits minute ; teeth short, blunt, finely but 

 obsoletely pectinated outside, and crenulated on the edge. Posterior 

 valve having a low, rounded callus ridge in place of the insertion- 

 plate, its edge unslit, finely and rather obsoletely striated, interrupted 

 by a deep rounded sinus in the middle behind. Eaves narrow, 

 solid. 



Girdle wide, bluish with inconspicuous dusky cross bars, slit 

 behind, its surface very densely covered with minute, closely 

 imbricating smooth convex scales (fig. 16.) 



Length 70, breadth 38 mill. ; divergence about 90, the young 

 more depressed. 



Port Jackson, Sydney, Watson's Bay and Middb II<irl>or, N. S. 

 Wales; Port Lincoln, S. Australia, under stones at extreme low 

 tide. 



