240 CORRIGENDA. 



PAGE 



94. T. excentrica, Park. Alter this name to T. affinis, Mill, and Sow. ; see p. 18", PI. XXI, fig, 7, and 



PL XXII, figs. 5, 5 a; also PI. XL, fig. 2. 

 96, line 23. Erase the sentence commencing " The Chloritic Marls." 

 115, T. Agassizii, line 23. Erase this name and substitute T. Upwarensis, p. 143, 

 126, line 7 from the bottom. For T. divaricata read T. disparilis. 

 138, line 12. For Petref. Sulc. read Petref. Suecc. 

 140. PL XXIII, fig. 7. Alter to T. Vicaryana, Lye. 

 159, line 2 from the top. For Shamford read Stamford. 

 1/4. Trigonia hemispheerica, var. gregaria, PL XXXIII, figs. 4, 5, 6. The examples of the smaU variety 



here represented have been incautiously sel?cted for their good condition of preservation. The 



ribbing is unusually large, and does not exemplify the more common, smaller, and less clearly 



defined examples with minute or variable ribbing. 

 211 Addenda. Erase line 13, commencing "at the base of the Upper Greensands," and substitute "in 



one of the lower beds of Greensand at that locality." The pebble bed here alluded to is at the 



base of the fourth or highest stage of the Trigonia-bearing beds. For its species, &c., see the 



stratigraphical table. 



EXPLANATION OF PLATES. 



PL IV, fig. 8. Erase the name T. Bronnii and substitute T. clavellata, Sow., young specimen, see 



pp. 23 and 209. 

 PL IX, fig. 1. Erase Wilts and substitute St. Adhelm's Head, Dorset. 

 PL IX, fig. 2. Alter T. incurva to T. Alina, Cont. Alter page 42 to page 193. 

 PL IX, fig. 3. Add T. incurva. 



PL IX, fig. 4. Alter the locality to St. Adhelm's Head, Dorset. 

 PL XIX, figs. A a, 4 b. The encircling costse upon the umbones of T. Manseli are not sufficiently 



numerous and minute. 

 PL XXI, figs. 2 a, 2 b, The encircling costse upon the umbones are not sufficiently linear and minute; 



this feature alone is sufficient to separate the form from T. gibbosa. 

 PL XXI, fig. 7. Add the words T. affinis. See page 187. 



PL XXIII, fig. 7. Alter T. Archiaciana, D'Orb., to T. Vicaryana, Lye. Alter page 140 to page 203. 

 PL XXXIV, fig. 1. T. sculpta. The figure of the right valve appears to represent an ante-carinal groove 



adjacent to the marginal carina. This is owing to the person who cleared the fossil from its 



matrix having heedlessly removed the posteal extremities of the costa, which should extend to the 



carina, as in other examples of the Costatce. 



The author desires to record his obligations to the artists engaged upon the plates of this Monograph 

 for the general care and fidelity to nature which they evince — the first nine plates by the late Mr. 

 Lackerbauer, the succeeding plates by M. Karmansky, the last plate by a son of the late Mr. Lacker- 

 bauer. The wood engravi^ngs up to p. 122 are by Mr. Dewilde ; the subsequent ones, by Mr. G. Shayler, 

 are carefully drawn exemplifications of foreign Trigonise. 



