195 



pare it, and the illustrations in Tryon's "Manual" are very 

 small; but the perforation on the slope and the internal sep- 

 tum coincide with its definition. One can see in different 

 individuals the varied aspects of the shell at successive stages, 

 first a depressed spiral shell with a simple aperture : then an 

 emarginula-like form, with a slit and slit fascicle; then a 

 rimula-like shell, with a perforation just above the margin, 

 continued as a narrow fissure to the border, and finally with 

 the fissure closed and the perforation complete. 



Modiola projecta, n. sp. PL xiii., figs. 12 and 13. 



Shell solid, narrowly oblong, inequilateral. Umbo direct- 

 ed forward at the junction of the first and second fourth of 

 the shell, approximate, round, inflated. Anterior dorsal mar- 

 gin with a uniform rounded slope, commencing just behind, 

 and within the apex of the umbo, over the front of which it 

 is reflected. Posterior dorsal margin straight, very gently 

 convex. Anterior end round : posterior end sloping convex. 

 Post-dorsal angle a very obtuse curve, post-ventral angle a 

 much smaller curve. Ventral border nearly straight, slightly 

 concave, almost parallel with the dorsal borders. Margin 

 simple, smooth. A groove increasing in width runs from the 

 limbo backwards within the post-dorsal border for three-quar- 

 ters of its length, formed by a stout, projecting: internal la- 

 mina, which widens for half its length, and then gradually 

 dwindles. The posterior muscle scar is rather deep. Of the 

 two oblique um.bo-ventral ridges the anterior is the more 

 distinct. Externally there are obsolete accremental striae, 

 and in the earlier stage distant, rounded, low, concentric 

 ridges, more marked towards the front. Traces of a dark epi- 

 dermis are present. 



Dim. — Antero-posterior diam., 10*9 mm. : umbo-ventral, 

 4*1 mm. 



Locality. — Off Beachport, 200 fathoms. One right valve. 



Modiolaria semiradiata, n. sp. PI. xiii., figs. l-I- and 15. 

 Shell oblong-ovate, ventricose. Umbo terminal, flattened, 

 directed forward, applied to the front end of the shell. Post- 

 dorsal border straight, short, thin, then faintly curved. Pos- 

 terior end round : ventral border straight, anterior end round. 

 Margin crenulated on the edge, with rounded teeth along the 

 curved part of the post-dorsal border and at both ends. The 

 ventral border shows no teeth, but probably because it is a 

 little eroded. A narrow oblique furrow runs between the 

 apex of the umbo and the adjacent front margin of the shell. 

 An inflated ridge runs from the umbo to the posterior end, 

 steep on the dorsal side, and gently sloping on the ventral. 



