256 AROIDJE* 



Shell thick, subrhomboidal, beaks anterior ; hinge with a few 

 oblique anterior teeth, and one or more long, laminar posterior 

 teeth, parallel with the hinge-line. 



cucuLLARiA, Deshayes, 1860. Shell elongated, suboval, moder- 

 ately inflated, radiately striated, inequilateral, beaks subanterior, 

 incurved, ver}^ close together, the hinge-area being very narrow 

 and almost wanting in some species ; hinge-line moderately 

 curved with a few shorter anterior and some longer posterior 

 fold-like teeth, arranged almost parallel to it ; numerous subequal 

 teeth are situated below the beaks. Area heterodonta^ Desh. 

 (cxxvii, 80, 81). From the Paris Basin. 



NBMODON, Conrad, 1869. Shell elongated, form resembling 

 Macrodon, but of thin structure; hinge-area very narrow, hinge- 

 line long, straight, or slightly curved under the beaks, " with 

 three linear teeth parallel with the anterior cardinal margin " in 

 the left valve, and with a double posterior lateral tooth, being 

 ver}^ long and linear ; under the beaks a few granular teeth are 

 present. M. Eufalensis, Conrad (cxxvi, 50, 61). Scarcely" dis- 

 tinct from the typical Macrodon. 



GRAMMATODON, Meek and Hayden, 1860. Appears to be dis- 

 tinguished only by the posterior muscular impression not being 

 raised upon a projecting lamina. Jurassic ; U. S. Type, M. 

 inornata, M. and H. 



Parallelopi PEDUM, Klein, 1153. 



Distr. — 2 sp. China. P. tortuosum, Lam. (cxxvii, 13). 



Shell subquadrangular or mytiliform, subequivalve, carinated, 

 twisted so that the straight hinge-line is oblique instead of 

 transverse to the beaks ; teeth numerous, middle ones smallest, 

 lateral ones larger and oblique. 



ScAPHULA, Benson, 1834. 



Distr. — Fresh water, India, Burmah. 



Shell thin, elongated, subtrapeziform, equivalve, very inequii 

 lateral, carinated behind ; valves covered with a thin, smooth 

 epidermis ; hinge edentulous in the centre, posterior teeth 

 laminar and branched. 



S, pinna^i Benson (cxxvi, 52), is found in the Ganges and its 

 branches, from Calcutta to Humeerpoor on the Jumna, 1000 

 miles from the sea. A second species has been found in the 

 river Tenasserim, Burmah. 



CucuLL^ A, Lamarck, 1801. 



Elym. — Cucullus, a cowl. 



Distr. — 2 sp. Mauritius, Nicobar, China. Fossil, 240 sp. 

 Lower Silurian; North America, Patagonia, Europe. G. con- 

 camerata, Mart, (cxxvii, 14). 



