PYCNODONTIDiE. 
203 
P. 1336. Smaller imperfect head and trunk, wanting the greater 
part of the fins ; Tarnhill, Tewkesbury, Gloucestershire. 
Egerton Coll. 
P. 5127. Very small imperfect trunk, with abraded scales showing 
the tubercular ornament in part; Langport, Somerset¬ 
shire. Par chased, 1886. 
Mesodon rugulosus (Agassiz). 
1825. Figure by C. Prevost, Ann. Sci. Nat. vol. iv. pi. xviii. fig. 18. 
1837. Pycnodus trigonus, W. Buckland, Geol. & Mineral., ed. 2, vol. ii. 
p. 45, pi. xxvii. c. fig. 3. 
1839-44. Pycnodus rugulosus , L. Agassiz, Poiss. Foss. vol. ii. pt. ii. 
p. 194, pi. lxxii. a. fig. 23. 
1839-44. Gyrodus trigonus, L. Agassiz, ibid. p. 232, pi. lxix. a. fig. 15. 
[Vomer; British Museum] x . 
1840. Pycnodus rugulosus , It. Owen, Odontography, pi. xxxiv. fig. 1. 
1844. Microdon trigonus, L. Agassiz, Tableau Gen. Poiss. Foss. p. xlii. 
(name only). 
1844. Pycnodus parvus, L. Agassiz, Poiss. Foss. vol. ii. pt. ii. p. 199 
(name only). [Mandibular dentition; British Museum.] 
1844. Pycnodus trigonus, L. Agassiz, ibid. p. 199 (name only). 
1844. Pycnodus latirostris, L. Agassiz, ibid. p. 199. [Mandibular 
dentition; British Museum.] 
(P) 1871. Pycnodus rugulosus, J. Phillips, Geol. Oxford, p. 179, woodc. 
xxxix. fig. 1. 
1871. Gyrodus trigonus , J. Phillips, ibid. p. 179, woodc. xxxix. fig. 7. 
1889. Mesodon rugulosus, A. S. Woodward, Geol. Mag. [3] vol. vi. 
p. 454. 
1889. Mesodon trigonus, A. S. Woodward, ibid. p. 454. 
1890-92. Mesodon rugulosus , A. S. Woodward, Proc. Geol. Assoc, 
vol. xi. p. 298, pi. iii. figs. 23-27, and ibid. vol. xii. p. 239, pi. iv. 
figs. 2-4. 
Type. Vomerine dentition ; Oxford Museum. 
A species of large size, known only by the head. External bones 
ornamented with coarse granulations, closely arranged ; maximum 
width of preoperculum exceeding half its depth. Teeth ornamented 
with a feeble rugosity radiating from an annular apical indentation, 
soon removed by abrasion; outline of teeth usually regularly 
rounded. Vomerine teeth closely arranged, those of the median 
series considerably broader than long and their breadth about equal 
to that of the two lateral series; an incomplete supplementary 
1 A vomer from the Bathonian of Pernigotti, Verona (de Zigno Collection, 
University of Padua), is also recorded under this name by F. Bassani, Atti Soc. 
Ital. Sci. Nat. vol. xxviii. (1885), p. 161. 
