MAZATLAN" BIVALVES BS 



116. GrouLDiA Pacifica, C. B. Ad. 



C. B. Ad. Pan. Shells, p. 275, no. 450, 



Tke only pair found (and that imperfect) was unfortunately 

 smashed just after it had been sketched. It was of a rich lus- 

 trous brown like Petricola robusta. The shell has aU shades 

 to a dingy white. About 18 odd valves were found, by no 

 means constant in their characters. The general appearance 

 is remarkably like a little fossil Astarte noticed in a communi- 

 cation made to the British Association, L'pool, 1854, (v. _ffie. 

 port, T^.7S,) flat, triangular (in that respect alone like TeUina 

 Bumeti) and with very distant ribs outside, These ribs are 

 generally sharp, but sometimes rather flat and rounded. The 

 anterior dorsal margin is concave in young specimens. The 

 sui'face of the shell appears under the glass, covered with fine 

 radiating strife ; but under the microscope these lines are 

 foimd to be simply the divisions between rows of parallel 

 oblong dots, which most resemble the strung figs of commerce, 

 and are laid in rows, side by side, over the surface of the shell. 

 These show through in very young specimens, and present a 

 most beautiful appearance. Inside, one valve has a long 

 anterior lateral tooth, a short distant posterior one, and 3 nar- 

 row divergent cardinal teeth, of which the middle one lies 

 between two broad pits, and the anterior joins on to the lateral. 

 The other valve displays a long posterior, and small distant 

 anterior lateral ; with 3 cardinals, of which one is the beginning 

 of the posterior lateral, the middle rises between two pits, and 

 the anterior is marginal, nearly obsolete. Muscular and paUial 

 marks distant from margin. Tlie largest valve measures 

 long. -16, lat. '18, alt. '05. 



iZ"a5.— Panama ; not common ; C. B. Adams.— M&z&tlan ; oflf 

 Chama; and Spondylus, very rare ; L'pool Col. 



Tablet 414 contains 4 valves, of different ages, and a fresh 

 fragment to shew the 'strimg-fig' structui-e. 



117. GOULDIA VAEIANS, n. S. 



G. t. minimd, subtrigona, subcequilaterali, forma plus minusve 

 angulato-rotundat&,plus minusve elongata ; alhidd, ptlus minusve 

 fiasco maculatA ; suhlrevi, striis incrementi, sive costis concev- 

 tricis paucis seu numerosis ; superjicie llneis granulosis radi- 

 antihus creberrimis ccdatd ; timbonibus subspiralibus, haud 

 conspicuis ; margine simplici, appresso ; dentibus lateralibus 



