28 



T. H. Withers — Cirripedes from the Chalk. 



angles to the tergo-lateral margin; tergo-lateral. margin nearly straight, slightly 

 rounded at the top towards the occludent margin ; umbo nearly in the middle of the 

 occludent margin, slightly nearer the rostral angle. The finely-marked and closely- 

 set growth-lines follow the outline of the basal and tergo-lateral margins, and on 

 reaching the groove, which runs almost parallel to the upper part of the occludent 

 margin, bend towards the margin. The inner surface of the valve along the inner 

 occludent margin rises up in a thickened band, being much thicker nearer the middle, 

 and forming a raised ridge overhanging the thinner part of the valve, thus making a pit 

 or depression for the attachment of the adductor scutorum. This thickened ridge, 

 especially near the middle, is marked with fine oblique lines. 



Remarks, and Comparison with other Species. Since the umbo in the 

 scuta described above is sub-central, and the growth consequently in 



Fig. 7. Loricula Darivini, H. "Woodward. Reproduced here to show position of 

 scutum (s), in which the umbo is situated nearest the apex, and the upper 

 part of the valve much attenuated, x 2 diani. Turouian, RhynehoneUa 

 ctcvieri-zone: Cuxton, near Rochester, Kent. 



Fig. 8a. Loricula expansa, Withers, sp. nov. External view of left scutum, 

 with umbo in sub-central position. x 4 diam. Upper Senonian, 

 Aetinoeamax quadratus-zone : East Harnham, near Salisbury, "Wilts. 

 ,, 8b. Id. Inner view of same, showing pit for adductor muscle. 



two opposite directions, it was at first thought that the plates belonged 

 to an undescribed form of Scalpellum allied to S. tuberculatum, Darwin 

 (1851, p. 43, pi. i, fig. 10), and S. cretce 1 (Steenstrup) (1837, p. 359 ; 

 1839, p. 399, pi. v, figs. 1-3), in which the umbo is also sub-central, 

 and not apical as in the more primitive fossil species of Scalpellum. 

 They differed much, however, from those species in the general shape 

 and ornamentation of the valves, and on comparing them with the 

 corresponding valves in Loricula it was at once apparent that they 

 agreed more closely with that genus. Examination of the scutum in 

 Loricula pulcliella, Gr. 13. Sowerby (1843, p. 260, figs. 1, 2), and 



1 Good descriptions and figures of the valves of this species are given by Darwin 

 (1851, p. 45, pi. i, fig. 11). 



