SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. 57 



gin of the shell beginning near the middle of the shell on the 

 posterior portion. (Fig. 2, 3, 4 and 5, plate IV.) 



Byssus: As remarked, adult shells are not furnished with a 

 byssus, the exception noted being extremely rare. The young 

 swim or dart through the water and are capable of forming a 

 byssus whenever they find themselves near to any object to which 

 they desire to become attached . When first formed the byssus 

 appears only like threads of mucous. 



Siphon: None. 



Month: Is situated above the foot, near the byssal opening in 

 the shell. The mouth is furnished with palpi (fig. 6, plate IV) 

 that are coarsely ridged and somewhat fan-shaped; these palpi 

 are joined to lips that are convolute or circinate in form. The 

 lips appear only as an extension of the palpi toward each other. 

 Besides being circinate they are coarsely striate and the outer 

 edges are scalloped. 



Kidney or Nephridium: The kidney lies on the anterior por- 

 tion of the adductor muscle, beginning under the liver region and 

 extending somewhat along the region of the gonad . The shape 

 of the kidney is elongate or tube like. (Fig. 5, plate IV, 

 fig. 8, plate V). There are two kidneys or nephridia. 



Gonad or reproductive organs: The gonad lying under the gills 

 are highly colored, the ovum of a bright orange, the sperm of a 

 deep cafe au lait color . These two glands are not separated but 

 form what appears to be an attachment and extension of the foot 

 — the sperm gland being the same color and apparently con- 

 nected with the foot. The reproductive organs do not com- 

 mence at the foot however, but occupy considerable space 

 above and between the foot and adductor muscle. The ova 

 encircles the kidney or nephridium and extends partly around 

 the adductor muscle. (Fig. 8, plate V). It is the 



presence of the highly colored gonad which gives the animal its 

 orange color. The spermatazoa gland partly encircles the ova 

 gland. The relative size and position of the hermaphrodite gland 

 varies in specimens; in one shell the ova may begin a little nearer 

 the foot and the sperm gland or testes, may occupy a smaller 

 space; this is obvious. Besides this hermaphroditic gonad, on 

 the liver, there is a network of greenish-white bodies — the green- 

 ish appearance probably due to the dark liver which shows some- 

 what through the semi-transparent substance, or at least, between 



