69 



common to observe young shells of three inches in length, and fully 

 grown ones of the same sort only one inch in length ; likewise, of 

 the well-known British Pholades there are individuals quite in a 

 young state of two inches in length, and perfectly formed shells of 

 the same species not more than half an inch long. For an instance 

 in demonstration I need only refer to the Phol. papi/raceus, so 

 abundant at Torquay, of which the young shells have been considered 

 by many as a distinct species and have been named by Dr. Turton 

 Phol. lamellosus. This varies in size exceedingly, so that it may 

 be obtained both in an incomplete and young state and in a fully 

 grown condition from half an inch to nearly two inches in length. 

 The circumstance of its having rarely occurred in an intermediate 

 state of growth, when the anterior opening is only partly closed 

 and the accessory valves only partly formed, led Dr. Turton and 

 others to persist in regarding the young and old as two distinct 

 species. Other similar instances will be shown in the course of the 

 present concise account of some hitherto undescribed species of the 

 same genus brought to England by Mr. Cuming." — G. B. S. 



Pholas cruciger. Phol. testa oblongd, scahra, marginibus un- 

 tied ventrali apertd, anticd dorsali rejlexd ; valvd accexsorid 

 soUtarid, posticd, transversa: long. 17, lat. 0*65, alt. 0"7 

 poll. 

 Hah. ad oras Columbiae Occidentalis et Americae Centralis. 

 In this species the anterior ventral opening is somewhat more 

 closed in some specimens than in others. It appears to form only one 

 accessory valve, which crosses the valves behind the umbones: the 

 dorsal margins are closed by epidermis. 



Found in three localities ; namely, in soft sandstone at half-tide 

 on the shores of the island of Puna in the Gulf of Guayaquil j in soft 

 stone at low water in the Bay of Caraccas ; both in West Columbia; 

 and in hard clay at a depth of thirteen fathoms in the Gulf of No- 

 coiyo in Central America. — G.B. S. 



Pholas Chiloensis, var. parva. Phol. Chiloensis, testd parvd, 

 tenutore: long. 1*6, lat. 06, alt, 0' 6 poll. 



Found in soft stone at a depth of seventeen fathoms at the island 

 of Plata, West Columbia.— G. B. S. 



Pholas subtruncata. Phol. testd ovato-oblongd, scabrd, postice 

 rotundato-subtruncatd, Icevi; margine anticd ventrali hiatu maxima ; 

 valvd accessorid soUtarid, anticd, lanceolatd, antice acuminatd : 

 long. 1-9, lat. 09, alt. 0-8 poll. 



Hab. ad Insulam Platse, Columbiae Occidentalis. 



Found in soft stone at a depth of seventeen fathoms. Very like 

 our British Pholas parva. — G. B. S. 



Pholas calva, Gray, MSS. Phol. testd ovatd, . antice retusd, 

 postice subacuminatd, hiante ; valvis singulis in areas tres divi- 

 sis ; areis, anticd scabriusculd ; intermedid epidermide corned Ion- 



'?/V, 



