40 



MARINE AND FISHERIES 



1-2 EDWARD VII., A. 1902 



DESCRIPTION OF PLATES I., II., Ill, IV. 



^ Plate I. 



Fig. 1. My a arenaria, natural size, from left side. The clam is represented in its 

 usual position buried in sand, siphons stretching to top of burrow. 



Plate II. , 



Fig. 2. Ditto from left ventral surface, to show foot, mantle, and siphons. 



Plate HI. 



Fig. 3. Ditto with left valve of shell raised backward.' Shows inside of left shell and 

 outside of left mantle fold. Foot and siphons retracted. 



Fig. 4. Mya arenaria, with mantle split from base of siphons ventromedially to above 

 anterior end and left half raised upward, to show contents of branchial cavity. 



Plate IV. 



Fig. 5. Mya arenaria. Natural size. Left shell, mantle, siphon walls and gills taken 

 off. Also left walls of kidney, pericardium, and abdomen removed, and the 

 contents of the latter dissected down to the intestine and crystalline style, to 

 show their course. 



F S — foot-slit, through mantle. 



F— foot. 



P G — pedal ganglion. 



C S — crystalline style. 



I — intestine. 



G G — genital gland. 



Ab— abdomen. 



BC — branchial cavity. 



B — branchife, right side. 



RS — retractor muscle of siphons, 

 showing through the right 

 wall of the mantle. 



M — mantle, split ventral wall. 



S— shell. 



VS — ventral siphon. 



Mo — mouth. 



CG — cerebral ganglion. 



St — stomach. 



L — liver. 



PG — position of pericardial gland. 



P — pericardium. 



U — umbo. 



V — ventricle. 



K — kidney. 



VG — visceral ganglion. 



PA — posterior adductor muscle. 



A — anus. 



PS — partition between siphons. 



DS — dorsal siphon. 



AA — anterior adductor muscle. 



Fig. 6. Nervous System of Mya arenaria, from Rawitz, reduced. 



Fig. 7. Ovum and Spermatozoon of Modiola modiolus, highly magnified. 



Fig. 8. Larva of Mya arenaria, showing shells, velum with cilia, kc, from Mead, mag- 

 nified. 



Fig. 9. Plant-food of clam. The first three are 'liatoms, the second three different 

 aspects of filamentous algrr, the crescent sh.iped one is a desraid, and the 

 spherical one the egg of Fucus. Highly magnified. These illustrate only a few 

 of the commonest forms from the intestine of the clam. 



Fig. 10. "C/am Zfoe," reduced. 



