1849.] SHARPE ON THE SECONDARY ROCKS OF PORTUGAL. 189 



Plate XIX. fig. 3 a. Upper valve. 



Fig. 3 5. Side view of the same specimen. 



Pecten Lusitanicus, n. s. Pl. XXIV. fig. 3. 



Shell oval, with the posterior and ventral margins rounded, and 

 the anterior margin angular ; valves unequally convex, ornamented 

 with strongly marked concentric lines of growth, crossed hy finely 

 impressed radiating lines, which become almost obsolete towards the 

 margin. Anterior ear covered with decussating lines : posterior ear ? 



Length If inch ; breadth 1^ inch. 



In limestone of the subcretaceous series between Torres Vedras 

 and Sobral. 



This Pecten has some resemblance to the P. obscurus^ Sow., 

 P. lens, Sow., and P. annulatus, Sow., which are oolitic species : it 

 is distinguished from them all by greater want of regularity, and by 

 the angular outline of the anterior margin. 



Perna? fragilis, n. s. Pl. XVIII. fig. 4. 



Subquadrate, anterior side a little excavated immediately below 

 the beaks ; gibbose anteriorly and gradually sloping posteriorly ; 

 shell very thin, with numerous, concentric, subsquamose lines of 

 growth : hinge ? 



Length If inch ; breadth If inch ; thickness |- of an inch. 



In the upper beds of the hippurite limestone near Lisbon ; rare. 



I have only one imperfect cast of this species, with portions of the 

 shell adhering to it. It differs from most of the species of Perna in 

 the extreme thinness of its shell, which might lead us to class it with 

 Inoceramus ; but the depression of the anterior part of the right 

 valve near the beak for the passage of a byssus unites it to Ferna. 

 In general appearance this species has considerable resemblance to 

 Perna polita. 



Plate XVIII. fig. 4. Right valve. 



Perna Lusitanica, n. s. Pl. XXIII. fig. 7 & 8. 



Subrhomboidal, very thick and heavy, marked irregularly by the 

 lines of growth : anterior side deeply depressed, and sloping inwards ; 

 posterior side slightly rounded away towards the palleal margin : 

 cardinal margin arched. Hinge-areas very broad, receding one from 

 another, and projecting anteriorly : ligamental hollows long and nu- 

 merous, broader than the intervening spaces, and slightly increasing 

 in width posteriorly, about twenty-four in number in a large speci- 

 men. Valves very thick, especially towards the hinge ; space occu- 

 pied by the animal nearly rectangular and very small in proportion 

 to the whole shell. Right valve larger and thicker, and with a 

 deeper hinge-area than the left. 



Found in subcretaceous limestone, between Enxarra dos Cavalheiros 

 and San Sebastian, and between Sobral and Torres Vedras. 



Nearly allied to P. Ricordeana, D'Orb., from which it differs in its 

 less regular and more rounded form and in the arched cardinal 

 margin. These differences are less visible in young than in old 



