448 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



11. Mopalia lignosa (Gould, 1846) 



1846. Chiton lignosus Gould, Proc. Bost. Soc. Nat. Hist., v. 



2, p. 142. 

 1846. Chiton Merckii Middendorff, Bull. Imp. Ac. Sci. St. 



Petersb., v. 6, p. 20. 



1846. Chiton Eschscholtzii Middendorff, id., p. 118. 



1847. Chiton Merckii Middendorff, Make. Ross., v. 1, p. 114, 



pi. 11, f. 5-6. 

 1847. Chiton Eschscholtzii Middendorff, id., p. 114. pi. 11, f. 4. 

 1847. Mopalia Simpsoni Gray, Proc. Zool. Soc. Lond., 1847. 



p. 69 (teste Carpenter; name only). 

 1852. Chiton vespertinus Gould, Moll. U. S. Expl. Exped., p. 



323, f. 426-426a. 

 1855. Chiton montereyensis Carpenter, Proc. Zool. Soc. Lond., 



1855, p. 231. 

 1862. Chiton lignosus Gould, Otia Conch., p. 3. 

 1862. Chiton (Chacto pleura) vespertinus Gould, Otia Conch., 



p. 230, 242. 

 1864. Mopalia lignosa Carpenter, Rep. Brit. Assoc. Adv. Sci.. 



1863, p. 530, 533, 554, 598, 648. 

 1879. Mopalia ciliata lignosa Dall, Proc. U. S. Nat. Mus., v. 



1, p. 304. 

 1893. Mopalia muscosa lignosa Pilsbry, Man. Conch., (1), v. 



14, p. 299, pi. 63, f. 58-59. 

 1919. Mopalia lignosa Chace and Chace, Lorquinia, v. 2, p. 42 



[2] (recorded from Pleistocene of Point Fermin, 



California). 



Diagnosis 11 : Valves of moderate thickness, barely beaked; 

 lateral areas usually distinct, bounded in front by a low, often 

 more or less obsolete diagonal rib ; head valve bearing 8 similar, 

 low, radial ribs; entire surface of all valves between ribs cov- 

 ered by a very fine latticed ribbing showing small pit-like 

 interstices, sometimes with sculpture nearly obsolete; traces of 

 brownish or grayish flammules sometimes still persistent ; 

 sutural laminae low and broad ; sinus narrow and rather shal- 

 low ; tegmental border in median valves with a distinct, round- 

 ed, median, beak-like projection in front; teeth of head valve 

 projecting, moderately long, sharply beveled and more or less 

 grooved at edges; teeth of median valves projecting, less dis- 



11 Description drawn in considerable part from recent specimens. 



