F. R. Cowper Reed — Fossils from Haverfordicest. 451 



The dimensions of two Eed. 5^1 specimens are the following : — 



I. II. 



Length 7*0 ... 8-5 mm. 



Width 13-0 ... 16-Omm. 



Plectambonitis papillosa, sp. nov. (PL XXIII, Figs. 13, 13a, 



14, 15.) 

 Description. — Shell small, transverse, broadly semicircular, twice 

 as wide as long ; widest at hinge-line ; concavo-convex to plano- 

 convex; cardinal angles sharp and angular, but not produced. 

 Pedicle valve weakly convex, flattened laterally; hinge-line straight; 

 beak small, inconspicuous, not rising above hinge-line ; hinge-area 

 narrow, inclined, with triangular delthyrium below beak. Brachial 

 valve slightly concave or nearly flat, flattened laterally ; beak very 

 small ; hinge-area very narrow, linear. Interior of pedicle valve 

 with small, short, divergent, divaricator scars, extending about one- 

 fourth or one - fifth the length of the shell ; teeth short, small, 

 diverging, supported by short dental plates. Brachial valve with 

 short crural plates and cardinal process (characters obscure). Interior 

 of both valves very coarsely papillose, the papillee large, more or less 

 elongated, and radially but irregularly arranged. Surface of valves 

 ornamented with regular, straight, fine radii of equal size, increasing 

 in number by intercalation of secondary rather finer ribs, about two- 

 thirds to three-fourths the length of the primary, to about 60-r80 

 ribs round the margin. 

 Dimensions (average). 



Length 3-0 mm. 



"Width 6-Omm. 



Locality. — Quarry at Upper Slade. 



Horizon. — Slade Beds. 



Eemaeks. — This pretty little species occurs in fair abundance at 

 Tipper Slade. It is certainly distinct from P. sericea, as its internal 

 characters prove. P. tenuissime-striata (McCoy) has much finer 

 and less conspicuous strige on the surface, and the coarse papillse 

 on the interior seem to be absent. The undetermined species 

 figured by Davidson^ from Llandeilo appears to bear a considerable 

 resemblance. ' Leptcena ' Grayce, Dav.,^ and ' LepV llandeiloensis, 

 Dav.,^ have somewhat similar ornamentation, but ours has not 

 a lobed shell like the former, and the interior of the latter is quite 

 distinct. The two valves are frequently attached and open, as is 

 often the case with P. plicatella, Ulrich,* an allied form from the 

 Utica group of America. There is no trace of cardinal spines in 

 any of our specimens, but the general characters of the shell recall 

 Chonetes. 



Atrvpa imbricata. Sow. (PI. XXIII, Fig. 16.) 



This species is stated by Davidson ^ to range up from the Bala to 



^ Davidson: op. cit., vol. iii, p. 330, pi. xlix, fig. 22. 



* Id., SuppL, vol. V, p. 171, pi. xii, figs. 23-25. 

 2 Ibid., p. 171, pi. xii, figs. 26-29. 



* Hall & Clarke: Palseont. New York, vol. viii, Brach., pt. 1, 1892, pi xva 

 figs. 34, 35. ' 



5 Op. cit., vol. iii, p. 135, pi. xv, figs. 3-8. 



