1G2 DIMYARIA. 



Magdala striata — The Striated Magdala. Plate 

 XVIII. fig. 12. Ovate-oblong, thin, pellucid, white; pos- 

 terior side rounded and the anterior side truncated and 

 gaping, with longitudinal striae and concentric wrinkles; in- 

 side perlaceous. One inch broad. Inhabits the British 

 seas. 



Genus 61.— MYATELLA.— J5/o!i)n. 



Generic Character. — Sub-parallelogramical, transverse, 

 anterior end truncated; the valves reflex, forming a hiatus; 

 umbo small, placed nearest the posterior end; with one 

 erect, broad, doubly channelled tooth in the left valve, 

 which locks into a corresponding cavity in the other, 



Myatella striata. — The Striated Myatella. Plate 

 XVI. tigs. 12 and 30. Subpellucid, white, of a delicate 

 texture, longitudinally striated; inside white, slightly re- 

 flecting a nacreous or iridescent hue. Length, half an inch ; 

 breadth, an inch. Inhabits the sea at Tenby in Wales. 



Genus 62 CRENELL A— ^row^n. 



Generic Character. — Oblong-ovate, equilateral, ventri- 

 cose ; beaks obtuse, slightly turned to one side ; hinge with- 

 out teeth, but with a flattened, slightly crenated plate in 

 each valve; the right valve with a triangular, horizontal, 

 projecting, reflexed plate, and the left one with an oblique 

 plate, both of which are slightly crenated. 



Crenella elliptica The Oval Crenella. Plate 



XVIII. fig. 13. Ovate, ventricose; with decussated striae; 

 greenish-yellow, inside nacred, the margins crenulated. One- 

 eighth of an inch long. Inhabits the coasts of Zetland and 

 Argyle. 



Genus 63.— SPHENIA Turton. 



Generic Character — Transversely oblong-ovate; slightly 

 tortuous ; hinge without teeth, but with the cardinal margin 

 flattened. 



