GENUS. GASTROCH./ENA. LAM. 

 Equivalve, somewhat wedge shaped, with a very large, 



oval, oblique, anterior opening between the valves ; 



the posterior extremity nearly closed ; hinge linear f 



marginal and toothless. 



G. MODIOLINA. Lam. 3. MYA DUBIA. Pen. 4. 

 t. 44. p. 82.Mont. p. 28. G. PHOLADIA. Turt. 

 B. t. 2./. 8, 9. p. 18. G. HIANS. Fl. p. 458. 

 Oblong, opaque, dirty white, finely striated concentri- 

 cally, margin from the beak to the ligament nearly 

 straight, then rounded anteriorly ; the oblique posterior 

 truncation extended beyond the middle of the ventral 

 margin; a narrow border in front of the beaks (which 

 are nearly terminal and rather prominent) where the 

 valves are in contact. i...l. In Limestone, near 

 low water mark. 



GENUS. GALEOMMA. TURTON. 

 Equivalve, equilateral, transverse, with a large open 



gape at the ventral margin ; hinge without teeth ;. 



ligament partly internal. 



G. TURTONI. Turton. in Z. J. 2. p. 362. t. 13. /. 

 1. Desk, in Lam. 6. p. ISO. Sow. f. 1, 2, 2.~ 

 Tumid in the middle and gradually sloping to tha 

 sides which are rounded and closed, dull milky white, 

 the surface covered with short close-set transverse 

 u 3 



