to N. abruptu, Dana, 1 from which species it liners in the 

 more central situation of the umbos, and the much shorter 

 nature of the anterior extremity, and also in the relative 

 proportions of the length to the height ; N. nbntpta being 

 much longer in proportion to its height than N. ovata. 

 From X. Waterhousei, Eth. 111., which is a fairly common 

 species at Gerringong, it differs principally in the ornamen- 

 tation, and there are no other species with which it can 

 readily be confounded. 

 Sol kxo ps is si\ 



Description— Shell soleniforme, long and narrow, and 

 somewhat expanded behind. Umbos small and situated 

 near the anterior extremity. Dorsal and ventral margins 

 parallel. Just anterior to the umbos the dorsal margin is 

 somewhat elevated, and below this the marked anterior 

 gape is slightly expanded. The posterior margin is also 

 probably gaping. Posteriorly the test has a tendency to 

 be keeled. The shell substance is somewhat thick for this 

 type of shell, and the ornamentation is concentric but faint. 

 The muscular impressions are obscure and hardly visible. 



Dimensions— Length 2} inches; height 1 of an inch ; 

 thickness of united valves iV of an inch. 



Loc. Burrier (D). 



Hor. Wandrawandian Series. 



Obs. Three specimens were found at Burrier, but not in 

 a very good state of preservation, and owing to this, the 

 species though evidently new is not yet named. 

 Platyschisma oculum, Sowerby. (Mitchell's Three 

 Exped. into Int. of Aus., pi. 2, f. 3 and 4). 



Loc. (1) Burrier (D), Grassy Gully (F); (2) Shoalhaven 

 River near Nowra (Q). 



Hor. (1) Wandrawandian Series ; (2) Nowra Grits. ^ 



1 Geol., Wilkes' U.S. Explor. Exped., p, <?.>*, Atlas pi. 7. f . 3. 



