69 



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

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

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

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

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

 in demonstration I need only refer to the Phol. paptfraceus, so 

 abundant atTorquay, of which the young shells have been considered 

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

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

 be obtained both in an incomplete and young statė 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 

 statė of growth, vvhen the anterior opening is only paitly 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 

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



Pholas cruciger. Phol. testd ohlongd, scabrd, marginihus an- y 

 ticd ventrali apertd, anticd dorsali rejlexd ; valvd accexsorid / "' '1 

 solitarid, posticd, transversd : long. 1'7, lat. 0*65, alt, 0*7 

 poli. 

 Hab. ad oras Columbiae Occidentalis et Americae Centralis. 

 In this species the anterior ventral opening is somewhat more 

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

 accessory vai ve, 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 Pūna in the Gulf of Guayaquil ; in soft 

 stone at low vvater in the Bay of Caraccas j both in VVest 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, 

 tenuiore: long. 1*6, lat. 06, alt. O' & poli. 



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

 of Plata, West Columbia,— G. B. S. 



Pholas st;btruncata. Phol. testd ovato-oblongd, scabrd, postice 

 rotundato-subtruncatd , leevi; margine anticd ventrali hiatu niaximo ; 

 valvd accessorid solitarid, anticd, lanceolatd, a?itice acuminatd : 

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



Hab. ad Insulam Platae, Columbiae Occidentalis. 



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

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



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

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

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



