MAZATLAN BIVALVES 113 



gensis) St. Domingo, Lamarck : W. Indies, Bristol Mus. 

 (A. clathrata) Fossil near Angers, Menard. 



Tablet 653 contains 6 very young pairs and 7, pairs of valves, 

 extremely young, the smallest measuring '04l>y "02, greatly 

 varying in outline. The teeth are at first very few in number, 

 and the internal ridge rather prominent. 654, a young pair 

 nestled, in situ, in fragment of Spondylus calcifer ; also 2 

 dried byssal feet. 655, 6 sp. young. 656, 8 adult sp., various 

 shapes. Two sp. will also be found in situ on Chaina (tablet 411.) 



195. BYSSOARCA SOLIDA, Sow. 



f 



Proc. Zool. Soc. 1833, p. IS.Milll. Syn. Test. Viv. p. 186. 

 Area solida, Rve. Conch. Ic. pi. 16, f. 106. Hani. Descr. Cat. 



p. 155, pi. 18, f. 54. B. M. Cat. D'Orb. Moll. p. 81, no. 716. 



C. B. Ad. Pan. Shells, p. 262, no. 423. 



This iinpretending species greatly resembles our B. lactea, 

 and a similar W. Indian species ; but differs from each by 

 well marked characters. In this, the ligament is in a very 

 narrow rhombus ; in B. lactea, in a broad one ; in the West 

 Indian it fills nearly the whole area. In B, solida, the hinge 

 teeth are nearly or quite obsolete within the ligament, even in 

 young shells ; in the other two species the teeth are in an 

 uninterrupted line. The surface also in B. solida is generally 

 decussated with concentric tubercles ; but this character is 

 not constant. Shape either flattened and produced, or short 

 and much swollen. Epidermis brown, thin. Byssal foot 

 extremely thin ; ventral margin not perceptibly gaping. 

 A finely grown specimen measures long. "35, lat. '56, alt. '28. 

 A swollen sp. '34, '47, '43. 



The largest sp. '46, '67, '46. 



JTab Under stones at Payta, Peru, Oumwig, IfOrbigny. 



Panama and Taboga ; not uncommon under stones near low 



water mark ; C. B. Adams. Mazatlan ; not uncommon ; 



L'pool Col. 



Tablet 657 contains 5 pairs and 1 valve very young, the 

 latter '03 across ; one pair is strongly decussated. 658, 5 sp. 

 scarcely decussated. 659, 3 do. flat growth. 660, 3 do. with 

 former margins projecting. 661, 3 do. swollen. 662, 3 do. 

 very much swollen, umbos distant. 663, 3 sp. shewing the 

 interior. 



