72 .Mr. 'I'. 11. AVithei^ on 



valves adjoining the carinal latus. Adopting Darwin's idea 

 as to the identity of tlie other valves, Thomson suggested 

 that these linear valves mnst represent two elements of a 

 carina. An alternative suggestion was that if the capi- 

 tulum was reversed the linear valve would be a reduced 

 scutum, the second latus a rostral latus, the first latus an 

 upper latus, and the scutum a carinal latus. This latter 

 view was suggested as possible, but further reasons were 

 given for his inclination to follow Darwin's ideas as to the 

 identity of the valves. 



Wyvillc Thomson's views have had no bearing on later 

 discussions, for his paper has been entirely overlooked, and 

 consequently his discovery of the split carina has passed 

 unnoticed. It was only through a book-seller's catalogue 

 that I came across the paper myself, and I then found that 

 the discovery of the s])lit carina in the genus, as now found 

 in the species S. puIchcUum and S. huworihi, was not a new 

 one. 



Except that later authors have differed as to the 

 numlier of valves in the capitulnm and as to the precise 

 names of the first or upper latus and the second or carinnl 

 latus, Darwin's purely tentative nomenclature has been 

 generally accepted without question. So far has this been 

 ihe case that no one has attempted to prove the identity ot 

 either of the valves. Any doubts, however, are set at r(>st. 

 by the new example of S. haworthi (PI. IV. fig. 2), for 

 in that specimen the valve called the scutum has its inner 

 surface cx])oscd, showing tlie pit for the adductor muscle, 

 thus proving that this really is the scutum. 



Accepting this, it follows that the other valves would 

 represent the upper latus, tergum, and carinal latus, and 

 that the two linear valves would equal the carina of other 

 cirripedes. Consequently the known valves would number 

 ten in all. This is the same number as given by Darwin 

 in his restoration, although the number is made up of 

 different elements, for, apart from the carina being split, 

 he included a rostrum. In none of the known specimens 

 has a rostrum been noticed, and in view of tlie structure of 

 the carina the imitrobability of a rostrum in the ordinary 

 sense Ijeing present is great. There does Tiot iippoar to be 

 any differentiation in structure of the uppermost siibscutal 

 plates of the |)ed uncle, and since they cannot be regarded as 

 part of the capitular region, a rostrum or valves Ijomologous 

 with it cannot be said to form part of the capitulum of 

 Straiiientum. 



