FOSSIL CIRRIPEDES. 531 



extension of the valve is due, not merely to the upward growth of 

 the intraparietes, but to the ahnost equal vipward and downward 

 growth of the valve from the umbo, the whole external surface of 

 the valve being ornamented. It is, therefore, probable that 

 species with an angularly bent carina, due to the upward growth 

 of the intraparietes, which is apparently the more primitive type, 

 existed even earlier than in the Upper Senonian *. 



Extreme interest attaches to the remarkably complete example 

 of /S. arcuatum from the Albian (Gault) of Folkestone, Kent, here 

 described and figured (p. 534, text-fig. 65, 6). To find so many 

 valves of the capitulum in position is a remarkable circumstance, 

 very few specimens of Scal])ellum having been discovered with 

 several valves associated. Those known up to the present come 

 from the Upper Senonian, and, with the exception of a single 

 incomplete capitulum of S. maxiimtm, belong to the species S.fos- 

 sula. This specimen, therefore, represents the only fossil species 

 of ScaJpellum obtained from below the Upper Senonian with any 

 considei'able number of valves in position. Previously described 

 species of Scalpellum from rocks below the Upper Senonian have 

 all been founded on detached valves, and in most cases on single 

 valves. Neither the upper latus, rostral latus, or rostrum, are 

 included in these descriptions, but are represented in the present 

 specimen. A further example of S. arcuatum (described, p. 533) 

 has furnished some scales of the peduncle, which so far are not 

 known in any species found below the Upper Senonian. *S'. arcu- 

 atum is the only representative of Scalpellum known from the 

 Albian (Gault) of England. 



Consequent on the discovery of the intraparietes in the carinte 

 of S. arcuatum, and &\ trilineatum, and since the cai'ina is the 

 typical valve of the genixs, it is here proposed to give fresh 

 diagnoses of those species and to describe the new material of 

 ^S'. arcuatum^ From the two examples of S. arcuatum it is 

 possible to construct a restoration of the capitulum, to which only 

 two valves are diagrammatically added (see text-fig. 65, 7, p. 534). 



Scalpellum trilineatum Darwin. 



1851, Scalpellum trilineatum C. R. Darwin, Pal. Soc. Monogr. 



Foss. Lepadidse, p. 38, pi. i. fig. 5. 

 1854. Scalpellum trilineatum C. R, Darwin, Ray Soc. Monogr. 



Sub-class Cirripedia, Balanidte, Synopsis et Index 



Systematicus, p. 633. 

 1854. Scalpellum tt^ilineatum J. Moriis, Cat. Bi-itish Fossils, 



2nd ed., p. 97. 

 1877. Scalpellum trilineatum H. Woodward, Brit. Mus. Cat. 



Brit. Foss. Crustacea, p. 143. 



* Since the above was written, two exceedinglj' small, angularlj' bent carina) 

 (length respectively VI mm. and 1"8 mm.) with the umbo subcentral, due to the 

 upward growth of the intraparietes, have been obtained by Mr. F. Mockler from the 

 Cenomanian (Chalk Marl) near Cambridge. The specimens are incomplete and 

 poorlj'' characterized, but of much importance as ■ showing that species with an 

 angularly' bent carina existed even so far back in tiineas the Cenomanian. 



