128 ON SOME NAKED AUSTRALIAN MARINE MOLLUSCA. 



cordate in outline, bearing at the tail, on the sole and in the 

 median line, a gland 30 mm. by 10 mm., distinguished from the 

 rest of the sole by its thick transverse rugosities and black colour. 

 Gill-plume tucked in between the mantle and the foot, a third as 

 long as the animal, bipinnate, folded down the centre so as to 

 expose one side only, the stalk without the pinnte within, attached 

 to the body as far as the 16th filament; pinnse 24, rapidly 

 increasing in length from the anterior to the 6th, thence gradually 

 decreasing to the posterior end, each filament attached beneath 

 for more than half its length ; midrib beaded at the junction of 

 each plumelet. Anus just within the tip of the gill and behind 

 the membrane upon which it is hung. External genitalia located 

 immediately before the branchia, wrapped within two oblong 

 flaps. 



The specimen above described was, with two others, dredged in 

 8 fathoms, about a mile south of the Sow and Pigs Reef, Port 

 Jackson, by the Marine Excursion of 17/12/92 of the Field 

 Naturalists' Society of N.S.W., and was presented to the Austra- 

 lian Museum by the Society. Another specimen, dredged off 

 Stokes' Point, in Broken Bay, N.S.W., has been presented by Mr, 

 Hill. Mr. Brazier also informs me that specimens of this species 

 from Port Stephens, N.S.W., have come under his notice. 



EXPLANATION OF PLATE. 



Fig. 1. — Dorsal aspect of Ovcanius hilli, from spirit specimen. 



Fig. 2. — Ventral aspect of ditto, the free edge of the foot bent over to 

 expose the anus, gill-plume and genitalia ; on the sole of the foot 

 the tail gland is shown. Both drawings slightly reduced and 

 photo-lithographed from the pen sketches of the writer. 



