120 MAZATLAN BIVALVES 



Hob. Mazatlan ; jun. abundant, rare adult, among sea weeds 



on Chainse, Spondyli, Ostrese, ^atellse, &c., or in the cavities 



of dead Lithophagi or Balani ; L'pool fy Havre Coll. 



Tablet 540 contains 5 pairs and 6 pairs of valves, smooth 



form. 541, 7 pairs and 6 pairs of valves, slightly lirate. 542, 



11 pairs and 7 pairs of valves, lirate, jun. 543, 7 pairs do. 



adult. 544, 2 pairs and a valve strongly lirate. 545, 2 sp. in 



crevices of Balanus and Lithophagus ; another Balanus has a 



crab in situ ; off Patella Mexicana. 546, a group in situ 



among Balani, on M. palliopunctatus. 547, 2 sp. one with the 



surface in concentric layers, like Crepidula Lessonii ; the 



other with young Nullipore. 



Tablet 548 contains 5 pairs and 4 pairs of valves, greenish 

 var., smooth form. 549, 7 pairs and 4 pairs of valves, finely 

 lirate. 550, 4 pairs and 1 pair of valves, strongly lirate. 551, 

 1 large valve, flat and broad. 



Tablet 552 contains 3 pairs and 2 valves, probably belonging 

 to this species. 



GENUS SEPTIFEB, Red. 



Vide Dunk. Com. Sep. et Dreis., Marburgh, 1855. Tichogonia, 

 pars, Rossmassler, 1835. 



169. SEPTIFEB CUMINCHI, Reel. 



Dunker, Monog. Sept. p. 8, no. 18. 



The few specimens found are too young to identify with 

 accuracy. They are covered with fine, granulose ribs, with 

 rather long bristly hairs rising up between. The umbonal 

 plate is scarcely perceptible in the smallest shells. Hinge line 

 crenate, as in M. multiformis. They closely resemble the 

 young of S. bilocularis, but geographically agree better with 

 the species quoted. The largest specimen measures only '16 

 in length. 

 jf a l Panama, Mus. Cuming. Mazatlan ; extremely rare, 



jun. on Spondylus ; IS pool Col. 



Tablet 553 contains 3 pairs of different ages. 



GENUS MODIOLA, Lam. ' 



Volsella, Scopoli, 1777. Modiola, Lam. 1801. Modiolus, 

 Risso, 1826. 



