Suhjamilies, Genera, and Subgenera — Recent and Fossil 185 



present work. The verge is figured rather longer than was observed in 

 specimens personally examined, but this organ is variable in form under 

 different conditions. The }x^culiar epiphallic enlargement of the vas 

 deferens is shown in Pilsbry's figure. The statement that the prostate 

 alveoli (diverticula) are in a single series needs emendation, for while they 

 ai^pear to be in a single series when viewed in position over the nidamental 

 gland, in a cross section they are seen to be composed of several brandies, 

 as figured on plate 38 (figs. 2, 3). The diverticula in the natural position 

 are hidden beneath the large diverticulum (as in fig. 1 in both plates 38 

 and 39) and the series appears simple. 



There is considerable difference between the genitalia of Menetus 

 operculaj'is and M. coopcri, particularly in the penial complex, in which the 

 form of the penial gland and the size of the eiiiphallus differ. This differ- 

 ence indicates that the two forms are distinct species. There is some slight 

 variation between specimens from British Columbia and California, but in 

 general the anatomical features are similar. 



Respiratory and Renal Systems. The pseudobranch of opercularis is 

 wide, somewhat folded or lobed and the rectum extends through the middle, 

 the anus opening at the lower edge (plate 38, fig. 4, P, A, R). There is a 

 large pneumostome. In cooperi callioglyptus (plate 39, figs. 2, 4), the 

 pseudobranch is rounded, somewhat lobed, and with a high ridge extend- 

 ing o^'er the length of the rectum (R) and running down the midde of the 

 pseudobranch as a low ridge. The anal opening is placed at the left side 

 of the pseudobranch. This ridge is also found in opercularis, but is not indi- 

 cated in the figure. The two forms of pseudobranch shown in figs. 2 and 4 

 on plate 39 indicate the amount of variation that may take place in two 

 individuals of the same species. 



The kidney (plate 46, fig. 7) of Menetus cooperi callioglyptus is short 

 and very wide (about 2 mm. long and 1 mm. wide). The ureter is a rather 

 long, narrow tube reflexed abruptly and directed upward into the mantle 

 cavity. The pericardium is about 1 mm. long. The lower part of the kidney 

 is very close to the mantle margin, the ureter being in contact with it. A 

 cross section of the kidney near the middle (fig. 8) shows the lumen to be 

 large, ovate, somewhat wider than high, the vein leading to the pericardium 

 much greater in diameter than the renal vein. There is no superposed ridge. 



Digestive System. The stomach region is elongated, the oesophagus 

 enlarged to form a crop, the gizzard rounded, and the pyloris rounded and 

 diminishing to the intestine which forms a complete loop around the 

 stomach, extends backward in the body, makes another loop around the 

 liver, and runs forward to the rectum, ending over the pseudobranch. 

 There is a long and narrow blind sac or caecum. The stomach region is 

 like that of Promenetus exacuous which is figured on plate 48, figs. 4, 5. 



The buccal sac is pyriform, with a large, rounded extension of the 

 radula sac at the lower, posterior part. The salivary glands are about twice 

 as long as the buccal sac and are much enlarged at the posterior end where 

 they are attached, the whole apparatus forming a loop. The oesojihagus is 

 enlarged to twice its diameter posterior to the buccal sac. 



The superior jaw of cooperi callioglyptus (plate 50, fig. 7) is arched, the 

 ends attenuated. There is a central rounded bulge on the lower margin. 

 The jaw is heavily, vertically striated. The side jaws are normal except 



