GENUS — SCALPELLUM. 217 



a functional mouth and prehensile cirri, may be separated 

 from 8. vulgar e^ ornatum and rutilum; but even between 

 these two little groups, 8. rostgratum is in some respects 

 intermediate, namely, in having three pairs of latera, and 

 more especially in the rudimentary condition of the 

 valves of its Complemental Male, and in the position in 

 which the male is attached to the hermaphrodite. The 

 three species in the second little group, namely, S. vulgar e, 

 8. ornatum, and 8. rutilum, are more nearly allied to 

 each other in all their characters, especially in the cha- 

 racters drawn from their Males, than are the other three 

 species. 8. ornatum and 8. rutilum are considerably 

 nearer to each other than any other two of the species. 

 Upon the whole I conclude that the six species must be 

 thrown either into five or into four genera (the first three 

 species making one genus), or all into one genus, and this 

 latter has appeared to me the preferable course. The 

 separation even of Scalpellum and Pollicipes, as already 

 stated, is hardly natural. The fact of these genera having 

 existed from a remote epoch, and having given rise during 

 successive periods to many species now extinct, is probably 

 the cause that the few remaining species are so much 

 more distinct from each other, than is common in the 

 other genera of Lepadidse. Whenever the structure of 

 the whole capitulum in the fossil species is well known, 

 and as soon as more species, recent and fossil, shall have 

 been discovered, then probably the genus Scalpellum will 

 have to be divided into several smaller genera. 



Description. — The Capitulum is much compressed, 

 and generally produced upwards; it is formed of from 

 twelve to fifteen valves, which are rather thin, and 

 with the exception of 8. ornatum, almost entirely covered 

 by membrane, bearing spines : the valves are seldom 

 locked very closely together. A sub-rostrum exists only 

 in 8. villosum, which species leads on to Pollicipes : in 

 8. vulgar e the rostrum is rudimentary and hidden. The 

 scuta, terga and carina, are much larger than the other 

 valves : these five valves seem to differ essentially from 



