1894.] NATrRAL SCIENCES OP PHIIjADEI.PHIA. So 



goual ril) which in Cox! exteutls from the apex of eacli median valve 

 to its hiteral slit;?. 



Acanthochites (Notoplax) speciosus H. Ad. PI. IV, tigs. 31, .12. 33. 

 Mnu. o1' ('(inch., X\', p. 3:.', I'l. 1, li.us. ^J3-26 (druAvii from type). 



This peculiar species may instantly be known by the wide, Crypto- 

 plax-like girdle, densely clothed with minute spines which are thick 

 and blunt for an Ac'iiifliorJilfex, and having inconspicuous sutural 

 tufts, not longer than the surrounding pile, but composed of finer, 

 whiter spicules. The tegmentum of each intermediate valve is tri- 

 angular, the girdle tissue forming spiculo.«e bridges at the sutures. 

 The dorsal areas are sharply defined, convex, and arcuately striated 

 b}'' growth- lines, l)ut show no longitudinal striie. The latero-pleu- 

 ral areas have round concave-topped pustules. Other notable fea- 

 tures are found in the tail- valve, which is very high, with vertical 

 posterior insertion-plate, and pear-shaped tegmentum. The sutural 

 laminte and insertion-plates are radially striated, and the posterior 

 valve has several slits, besides the usual pair. The tegmentum of 

 the head- valve is small, extending hardly half the length of the front 

 slope of the valve. The figure.* are drawn from a specimen from 

 St. Vincent Gulf, furnished by Mr. W. T. Bednall. It has been 

 known hitherto from Tasmania (Cuming coll.) and Flinder's Island 

 (Jos. Milligan). 



Acanthochites (Notoplax?) Matthews! Eednall and Pil.shiy. PL IV, figs. 

 •27, 28. 2i), 30. 

 Nautihus ^'II, p, 120, Feb. 1S94. 



Shell elongated, narrow, moderately elevated and carinated, the 

 side-slopes straight. Valves of a delicate flesh tint, each having 

 several concentric, forward- converging, zigzag bands of olive-brown. 

 Girdle hoary, with white sutural pores. 



Valves i to vii bave the posterior (sutural) margins concave, the 

 small beaks slightly projecting. Dorsal areas narrow, very convex, 

 but not raised at the edges, delicately striated longitudinally. Side 

 areas divided into pleural and lateral tracts by a small curved dia- 

 gonal riblet; the pleural tracts sculptured with loiigitndinal rihlets 

 (about fifteen on each side), flattened and faintly crenulated; as 

 they cross the diagonal rib these riblets bend abruptly upward, 

 passing obliquely across the lateral areas, upon which they are more 

 distinctly crenulated or broken into pustules, especially near the beak 

 of each valve. Anterior valve having five low radial elevations, 



