CHIEFLY OF THE UNITED STATES. 31 



scribed by Mr. Rang as Anodonfa Chaiziwna, but which I have al\va_>s suspected to 

 be of the genus Spatha, but it must be remembered that he does not describe or 

 figure syphons. 



Spatha modesta. PI. 1.^), fig. 3-5. 



Testa subsulcata. traasver.sa, .siibcompressa, inaequilaterali, postice et antioe rotunda ; valvulis tenuibus ; 

 natibus parvis. promiuulis, ad apices miuute undulatis ; epiderinide tenebroso-olivacea, eradiata, niti- 

 da ; margarita oajruleo-alba et valde iridesceute. 



Shell subsulcate, transverse, somewhat compressed, inequilateral, round behind and 

 before; valves thin ; beaks small, a little prominent and minutely undulate at the 

 tips; epidermis dark olive, without rays, shining; nacre bluish white and very 

 ii'idescent. 



Proo. Acad. Nat. Sci.. 1864, p. 109. 



Hub. — Fresh waters near Mozambique, Africa, John Kirk, M. D., of the Zambezi 

 Expedition. 



My cabinet. 

 Diam. -6, Length -7, Breadth 2-2 inches. 



Shell somewhat .sulcate, transverse, somewhat compressed, inequilateral, round be- 

 hind and before ; substance of the shell thin ; beaks small, a little prominent, pointed 

 and minutely undulate at the tips; ligament long, thin and bright brown; epidermis 

 dark olive green, without rays and shining; umbonial slope slightly raised and 

 rounded; posterior slope very narrow, long, elliptical, slightly carinate and furnished 

 with two lines on each valve from the beaks to the posterior margin ; anterior cica- 

 trices distinct, very large and very slightly impressed ; posterior cicatrices distinct, 

 large and very slightly impressed ; dorsal cicatrices placed across the centre of the 

 cavity of the beaks ; cavity of the shell shallow and wide ; cavity of the beaks very 

 small ; nacre bluish white and very iridescen ^^ ' 



Remarks. — This small and modest species is allied to S. ccelestis (nobi.s), but may at 

 once be distinguished by being less transverse, and in having a rounded posterior 

 margin. It is evidently a smaller species. Like that species the nacre is bluish, and 

 there is a deposit in the cavity of the beaks which gives a greenish blue color to the 

 tips when the epidermis is worn off. The specimen before me is without rays — 

 younger and more jierfect specimens may sometimes have them. The furrows on 

 this are well marked only on the anterior half and on the margin of the other parts. 

 It is greatly to be regretted that we have not the soft parts to examine. 



