part 3] THE teias of ^ew Zealand. 209 



curved below, and broadly rounded behind. The surface of the 

 «hell is gently rounded, with fine, closely-set growth-lines, inter- 

 rupted in places, especially towards tlie margin, by a larger growth- 

 furrow. There is no radial sculpture or ridge. Length = 42 inm. ; 

 height = 29 mm. ; depth of the left valve — 11 mm. 



Locality and horizon. — Bed c, Otamita, Hokonui Hills. 

 I collected a fine left valve and a smaller double- valved specimen, 

 both with the shell jDreserved. Carnic. 



Ke marks. — This form differs from A. oval is in its much thicker 

 shell, more elongated shape, and larger size. The fine concentric 

 growth-lines recall those on a specimen of A. grieshachi illustrated 

 by Bittner; but the beaks are more anteriorly situated, and the 

 shell is apparently thicker. I could not ascertain the characters 

 of the hinge-area in my specimens. 



Megalodo?^ globulaeis, sp. nov. (PI. XXI, fig. 17.) 



Shell thick, rounded, tumid, and inflated, especially towards the 

 hinder margin ; the two valves together form a rather globular 

 shell. The beaks are anteriorly situated, strongly directed for- 

 wards, produced to a point, and nearly touch one another. Below 

 them is a deep, false, lunular depression. The shell-margin 

 is gently rounded behind and below, but is slightly produced 

 anteriorly below the lunule. The growth-lines are closely set and 

 €oarsely marked, and the growth of the shell is somewhat inter- 

 rupted and irregular. The anterior muscle-scar is fairly strongly 

 marked. 



One specimen is 23 mm. long, 27 mm. high, and each valve is 

 15 mm. deep. A rather smaller right valve is 20 mm. long, 

 18 mm. high, and 8 mm. deep. 



Locality and horizon. — I collected the casts and impressions 

 of two specimens (one with both valves together and part of the 

 shell remaining) on the north side of the entrance of the Wairoa 

 Gorge in greywackes below the 3I}jtilus-prohlemaficiis Bed. The 

 other, a right valve, occurred a little way up the Gorge in the 

 Mi/tilus-prohlematicus Bed. Lower Carnic. From both of these 

 gutta-percha squeezes were made. 



Remarks. — There seems to be no doubt that this shell is a 

 Megalodon, the hinge-plate is thick and heavy ; but I could not 

 see the disposition of the teeth, neither could I ascertain whether 

 the valves were quite equal or not. 



Pseudoplactjin'Opsis placextoides, sp. nov. (PI. XXI, figs. 14 

 &15.) 



Bittner uses this generic or subgeneric name for shells outwardly 

 resembling Placuuopsis, but wherein the hinge-apparatus par- 

 takes of the character of that of Spo)ulijlus or Plicatula, and is 

 formed by two ridges or auricular crura which diverge below the 

 beak. 



The shell here described comes under this generic definition. 



