602 DR. R. V. ERLANGER. 
4. Patella cerulea and Tectura spec.? 
Special attention was given to Patella, as my results are 
absolutely contradictory to those of Ray Lankester (18, 19, 
20) and Cunningham (6). Patella coerulea is the only 
species of Patella found in the Gulf of Naples, and is the 
same which Cunningham has studied. I therefore do not 
doubt that the study of Patella vulgata would lead to 
the very same conclusions. 
Perrier (23) has evidently neglected the right, reno-pericar- 
diac duct in Patella, as he neither describes nor figures it. © 
The shape and position of both renal organs are displayed 
in fig. 14, drawn from a hardened specimen after removal of 
the shell, hood, and dorsal pigment. The pericardium (Pe.) 
lies to the left and at the hinder end of the mantle cavity (M.). 
Its position and shape have been accurately described by Ray 
Lankester (loc. cit.) and Wegmann (28), who has written a 
short but valuable monograph of Patella vulgata, unfortu- 
nately paying but little attention to the relations of the kid- 
neys and the pericardium. 
The little or left kidney (N/.) lies immediately to the left of 
the pericardium, between it and the right kidney (Nr.), which 
covers very nearly the whole of the visceral mass. The 
papille of the kidneys lie on either side of the anus (A.) 
(Xr. and X/.), and may be easily found when the hood or 
anterior mantle-flap has been removed. 
Sections (transverse and horizontal) show that the kidneys 
are situated on either side of the rectum (2.) (fig. 25 a) (Nr. 
and W/.). Their general histological appearance closely re- 
sembles that of Fissurella. It 1s a well-known fact that the 
rectum does not perforate the ventricle and pericardium in 
Patella, so that the rectum, the left kidney, and the anterior 
part of the right kidney are situated entirely to the left of ” 
the pericardium. The blood-sinuses of both kidneys are, as 
Perrier (23) has shown, in relation with the auricle of the 
heart, while in Fissurella, Haliotis, and Trochus this 
statement can only be applied to the left kidney. 
