SMITH ON THE AGE OF THE TERTIARY BEDS OF THE TAGUS. 419 



in general, a very small intermediate rib between the principal ribs 

 corresponding to a depressed line on the broad ribs of tlie convex 

 valve. Judging from the deeply depressed broad ears, the other valve 

 of this species should be very deeply convex. 



Pecten Josslingii, Smith. 



Figs. 10, 11, 12. 



P. testa valde ingequivalvi, subsequilaterali, valva altera plano-subconcava, costis 

 radiantibus 16, utroque latere angulatis, interstitiis latis ; altera alte convexa, 

 umbone recurvo, magno, costis radiantibus 18, latis, rotundato-planulatis, inter- 

 stitiis angustioribus ; auriculis magnis, sequalibus, Isevibus. Long. 2*0, lat. 0*9, 

 alt. 2-1 poll. 



Like Pecten fuscatus of Gray and Pecten arcuatus of Brocchi (to 

 both of which this fine species bears some resemblance), one of its 

 valves is remarkably convex ; its umbo is very large and recurved, 

 more than in either of those species, so much so, that a single imper- 

 fect convex valve has been taken for a Cardium. The interstices of 

 the flat valve correspond in width Avith the ribs of the convex valve, 

 and vice versa. 



Pecten fraterculus. 



Figs. 13, 14. 



P. testa insequivalvi, sequilaterali, Isevi, radiatim costata, valva altera convexa, 

 costis 20, utroque latere rotundato angulosis ; interstitiis angustioribus ; altera 

 subconvexo-plana, costis 18 angustis, rotundatis, interstitiis latioribus, auriculis 

 mediocribus. Long. 1-9, lat. 0-55, alt. 1'9 poll. 



• The general form of this species is much like that of P. maximus ; 

 it appears however to be sutficiently distinguished from that species 

 by the number and form of its ribs, as well as by its being destitute of 

 radiating strise. From the Almada beds, and also from the blue marl 

 at Adi9a, to the south of Lisbon. 



Pecten expansus. 



Fig. 21. 



P. testa suborbiculari, valde expansa, insequivalvi, sequilaterali, Isevi, radiata; valva 

 altera plano-subconvexa, latei'ibus paululum reflexis, altera convexiori, lateribus 

 pariter deflexis ; auriculis magnis. Long. 5*5, lat. 1'3, alt. 5*0 poll. 



Certainly very different from P. Pleuronectes and Japonicus, Lam., 

 and much nearer to P. Laurentii in general form, as well as in the 

 size of the ears, which are double the size in this and P. Laurentii 

 that they are in P. Pleuronectes and P. Japonicus. In form our 

 shell resembles P. cristatus of Goldfuss, t. 99. fig. 13; his expres- 

 sion, '* auriculis in margine cardinal! valvse dextrse spinosis," proves 

 that it cannot be the same. 



Pecten acuticostatus. 



Fig. 18. 



P. testa suborbiculari, valva altera convexa, costis radiantibus 20, acutis, elevatis ; 

 lateribus costarum interstitiisque concentrice striatis ; auriculis magnis, tenuiter 

 radiatim costatis. 



A fragment only of one valve of this species has been found ; it 



