

152 Fossils from Australia. 



served cast, only a small portion of the original shell remains, from 

 which it appears that the surface was smooth, and marked only by faint 

 lines of growth. — Harper's Hill. 



Pentadia, (nov. gen.) — This name is proposed for singular flat fos- 

 sils, which have one side quite smooth, the other delicately and closely 

 marked with parallel subcrenulate ridges having the angles of a regular 

 pentagon and concentric. Two of the specimens are casts of the exte- 

 rior, and the other is a calcareous petrifaction. As the last mentioned 

 is quite solid, having the oblique cleavage of many calcareous fossils, 

 (the spines of Echini, &c.) it is evident that the original was solid, and 

 could not have been a Porpita, which one of the specimens somewhat 

 resembles. And since, besides, there is no appearance of a mouth or 

 any opening, or organs of motion, and the form varies very much, we 

 may infer that the fossils were an internal secretion probably of some 

 mollusk, and more allied to the cuttle-fish bone than any thing else we 

 can suggest. The first species here described has much the" appear- 

 ance of a Spatangus. 



8. Pentadia spatangus. — Form pentagonal or approximately twelve- 

 sided, suborbicular, with five broad and rounded folds (one largest) 

 radiating from the centre. The concentric pentagonal markings have 

 the five angles at the centres of the triangular sections ; and at the cen- 

 tres of four of the sides of the pentagon, there is a reentering angle 

 Jhameter 2 inches ; thickness £ inch.— lllawarra. 



9. Pentadia reniformis.— Resembles a single segment of the prece- 

 ding, with a broad lateral wing-like prolongation, nearly as large as the 

 segment. It is quite thin, and its shape is reniform, though somewhat 

 arcuately flexed. The specimen is undoubtedly a perfect individual. 

 Length^ ln ch; breadth 1£ inch ; thickness I [me.—Illaioarra. 



1U . lentadia trigona.— Shape triangular, slightly arcuately flexed- 

 is thicker than either of the preceding, and has a rounded margin- 

 It resembles the last in its markings, having the same angle of inter- 

 section (that of a pentagon) between two sets of parallel lines. 

 Breadth 1 inch ; thickness £ inch.- lllawarra. 



1 1. Lingula ovata.— Quite small, regularly broad ovate, acute at beak, 

 margin not at all truncate; valves thin, very convex : surface smooth 

 vvith faint concentric lines of growth.— Dimensions, from the beak to 

 the opposite margin £ of an inch ; transverse line a fourth less.-Very 

 near the L lata of Murchison, (Sil. Syst., pi. 8, fig. 11,) but not at all 

 squarish."— lllawarra. 



1'2. Terebratula amygdala.- Oblong ovate, attenuate above, thickest 



about the centre, valves about equally and regularly convex, inferior 

 margin arcuate, ventral valve very regularly ovate in outline ; beak re- 

 flexed close to apex of ventral valve; aperture round and rather large; 

 line of junction of valves in side view almost straight, very slightly bent 

 above, the cardinal edges being little concave; surface smooth with a 

 few concentric folds and some faint radiations.— Cardinal angle 82 c 

 height 1£ inch ; breadth &% H. ; thickness T *% H. Near the T. has- 

 tata. — lllawarra. 



13. Terebratula elongata.—( Vemeuil, Paleozoic Rocks of Rus ) 

 Jn^j P '?' g - 9 -)— Scarcely differs from this species as described 

 and figured by Verneuil.— lllawarra. 



