Vol. 70.] THROUGH THE AXDES OF PERU 1XD BOLIVIA. 9 



Palaeontological Notes. 



With one or two exceptions, the fossils obtained from the stra- 

 tified beds of the Moito are badly preserved, and it is impossible 

 to make exact specific determinations. The general assemblage, 

 however, points to a Bathonian facies at the base, with a transition 

 into Callovian and Oxfordian, and possibly still higher beds, at the 

 summit of the hill. 



Faunal List. 



Terebratula cf. maxillata Sow. Gryplxsea sp. 



Rhynchonella cf. obsolete. (Sow.). Macwceplialites sp. 



Flabellothyris sp. Cosmoceras aff. ornatum Schloth. 



Pecten sp. Serpulites. 



Modiola sp. Cidaris spines. 

 Posidonomya escattiana, sp. nov. 



POSIDOX03ITA ESCUTTIA3~A, sp. 110V. (PI. Till, fig. 7.) 



This species, which occurs abundantly in the black shales sur- 

 rounding the ' pillows ' in the main mass of lava, has the following 

 characters : — Shell thin and transversely oval, though slightly 

 oblique ; very gently convex, the greatest convexity being along 

 a line drawn from the umbo to the lower posterior angle. 



Hinge-line straight, not much shorter than the greatest width 

 of the shell. Both anterior and posterior borders rounded. 

 Umbones small, situated at about a third of the length of the hinge- 

 line from its anterior end. 



Surface ornamented with concentric flattened folds separated 

 by grooves. These become gradually broader towards the lower 

 border, and are crossed radially by irregular pustulose wrinkles, 

 ill-defined in the young shell, but becoming more pronounced with 

 age. The wrinkles on' one fold at first tend to be distinct from 

 those on the next, but towards the lower margin frequently pass 

 across the intervening furrow. They are but feebly developed on 

 the posterior and anterior borders of the shell. 



I have been unable to find any other example of the genus 

 bearing this peculiar type of ornamentation, which therefore 

 appears to be sufficiently characteristic to warrant the introduction 

 of a new specific name. 



Macrocephalites sp. (PI. VIII, figs. 1 a & 1 b.) 



The general form of this species is that of a small Macro- 

 cephalites, showing certain affinities with the Sphserocerates. 



The whorls increase in size rather rapidly, and, though not very 

 deep, are considerably involute, being thus somewhat semilunar in 

 cross -section. They possess a Stephanocerate type of ornament. 

 The ribs are numerous and fine, but with no conspicuous thickening 

 along the umbilical margin. The umbilicus is deep and crateriform, 

 with steep sides. The suture-lines, although indistinct, do not 

 appear to be very complicated. 



