824 Prof. W. Thomson on a new Fossil Cirripede. 



The tergum is broadly triangular, inserted exactly as in Dar- 

 win's restoration, between the first and second latera ; the lines 

 of growth proceed downwards from the upper left-hand acute 

 angle, with an elbow towards the obtuse angle, the elbows form- 

 ing an obscure line nearly parallel to the upper margin. 



The peduncle is mailed, as in Loricula pulchella, with imbri- 

 cated plates arranged in transverse and longitudinal rows. 



In the part of the side of the specimen preserved, the first 

 seven upper transverse rows are alike. From left to right, a 

 short, nearly square plate corresponds to the base of the linear 

 left-hand valve ; the left edge is straight and vertical, the right 

 slightly prolonged, and passing beneath the end of the plate 

 next it in the row, which is longer and narrower, corresponding 

 to the base of the second latus. The third plate is much longer 

 and narrower, following the basal outline of the scutal latus, -a 

 depression receiving its projecting angle, then passing on and 

 forming an umbo opposite the junction of the first latus with 

 the scutum, and continued beneath the scutum. Under the 

 middle of the scutum all these plates are unfortunately broken. 

 In all the seven upper rows this plate becomes much narrower 

 towards the rostrum, — this narrowing, rather than the absence 

 of any of the plates of the vertical rows, seeming to account for 

 the depression of the capitulum towards the rostral aspect. 



The right-hand portion of the upper rows is lost. Doubtless 

 they ended, as in L. pulchellu, in another row of small square 

 plates. In the eighth row, the third plate is divided into two, 

 the junction replacing the umbo opposite the scuto-lateral su- 

 ture. The end of the third plate passes beneath the fourth. 



From the tenth row downwards only two vertical rows are 

 partially preserved, the third and part of the fourth. The third 

 longitudinal series seems to be complete, and contains sixteen 

 plates. In the fifteenth and sixteenth transverse rows the plates 

 are smaller and more crowded, the sixteenth forming a distinct 

 ring of attachment. The lines of growth of the peduncular 

 plates are transverse : a slightly elevated ridge, nearly bisecting 

 the plate, indicates the extent to which the plates of each lower 

 row overlap those of the row above it. 



Length 1 inch; breadth 0*5. Closely allied to Loricula pul- 

 chella. One specific distinction is very evident, — the fusion of 

 plates corresponding to the scutum and the scutal latus in the 

 upper rows of the peduncle. 



Loricula MacAdami seems to have been gregarious. Some 

 obscure fragments of others of a group are scattered through 

 the matrix. 



With the additional information derived from the specimen, 

 the structure of Loricula is certainly more anomalous than ever. 



