1,853.] ■ RIBEIRO AND SHARPE — BUSSACO. 149 



growth, between which the surface is covered with closely set equal 

 concentric lines : muscular impressions equally strong : cardinal 

 teeth unequal, about twelve anterior and six posterior meeting at 

 the umbo ; the largest in the middle of each series. 



Length 0'3, breadth 0'4 of an inch. 



Abundant in the lower division of the Lower Silurian formation of 

 the Serra de Bussaco. ^ 



Named after Dr. F. A. Pereira Costa, of Lisbon. 



Plate IX. fig. 4. a. Exterior, h. Interior. 



NucuLA Ci^, n. s. Pl. IX. fig. 5. 



N. testa transversim ovata, concentrice lineata; impressione musculari 

 postica maxima ; dentibus cardinis anticis 9 parvis, posticis 10 majoribus 

 insequalibus. 



Shell transversely ovate, covered with fine concentric lines : ante- 

 rior muscular impression moderate, posterior very large : hinge-teeth 

 in two sets separated by a vacant space at the umbo ; anterior ten, 

 small ; posterior nine or ten, long and unequal. 



Length 0'4, breadth 0*6 of an inch. 



Found in the lower division of the Lowpj;^lurian formation of the 

 Serra de Bussaco^ ~ 



Named in honour of Don P. Cia, of Madrid. 



Plate IX. fig. 5. a. Exterior, h. Interior, c. Hinge-teeth. 



NuCULA RlBEIRO, u. s. Pl. IX. fig. 6. 



N. testa triangulari-globosa, concentrice eleganter lineata, dentibus cardi- 

 nalibus 30 insequalibus continuis. 



Shell globose with a depression in front of the beaks ; elegantly 

 marked with ten or twelve equidistant strong rings, between every 

 two of which are five or six equal close-set concentric lines ; anterior 

 muscular impression large and deep, posterior one faint : hinge-teeth 

 about thirty, continuous, five or six long teeth on the anterior side ; 

 about fifteen very small teeth in a curve round the umbo, and about 

 ten of intermediate size on the posterior side. 



Length and breadth f of an inch. 



Found in the lower division of the Lower Sjl urian fo rmation at the 

 Portela de Loredo, in the Serra de Bus8acQ,_and named after Senhor 

 Carlos Ribeiro. 



Plate IX. fig. 6. a. Exterior, h. Interior, c. Hinge-teeth. 



NucuLA EzQUERR^, n. s. Pl. IX. fig. 7. 



N. testa ovata, lineis concentricis inconspiciiis ; dentibus cardinis sub- 

 sequalibus, anterioribus 6, posterioribus 15. 



Shell ovate, marked with some inconspicuous concentric lines ; 

 muscular impressions slight : hinge-teeth about twenty, fifteen pos- 

 terior, five anterior, separated by a small vacant space on the anterior 

 side of the umbo, those below the umbo small, the rest nearly equal. 



Length \, breadth f of an inch. 



