PROTKOLEPAS BIVINCTA. 601 



described is, that the ducts, in both cases formed by the 

 prolongation of the coat of an ovarian receptacle, are here 

 protected by a thick outer membrane, lined, at least in the 

 upper part, by corium ; whereas, in the Lepadidse the two 

 ducts are included within the peduncle, and are therefore 

 protected by one common membrane, lined of course by 

 coriumi ; and this membrane, we shall presently see, is 

 homologous with that separately investing the two threads. 



The antennas differ remarkably little, considering the 

 anomalous character of the mature animal, from the same 

 organ in other genera ; they come nearest, perhaps, to the 

 antennas of Ibla. The length of the disc (y, fig. 1) and 

 great succeeding segment (/) together is ^ihs of an inch. 

 The lower segment has its basal articulation only slightly 

 oblique, showing that, as in Alcippe and Ibla, it was 

 probably articulated near the anterior end of the pupal 

 shell : it is of nearly the same width throughout.* The 

 disc {$) is remarkable from its great proportional length; 

 it is hoof-shaped, with the outer side rather protuberant, 

 and the end pointed. The ultimate segment (h) is of 

 moderate size : as in Ibla, it has a shoulder or notch on 

 its inner side near its end, bearing two long spines ; and 

 probably there were originally three or four spines on the 

 square broad upper end, but these have been broken. This 

 segment is articulated unusually near to the end of the disc. 



The foregoing remarks on the two threads by which 

 Proteolepas is attached, are, independently of their relation 

 to this individual animal, of considerable interest. In 

 my volume on the Lepadidae, I have stated, after repeated 

 and rigorous examinations (for I was well aware how 

 singular the facts were), that in Vonckoderma aurila and 

 in some other genera, the cement-ducts, which entered 

 the pupal antennae, could be traced till they joined a 

 gland, the coat of which gland was absolutely continuous 

 with the coats of the adjoining and continuous ovarian 

 tubes, of which it was only a modified portion ; and what 



* As I have given the measurements of the antennae in so many genera, I will 

 give these : second (/, fig. 1) segment, g^ths of an inch in length, and f^ths in 

 width. Disc, souths in length, and goooths in width. Ultimate segment, goooths (?) 

 in length, and soJoo^hs (?) in breadth. 



