NOTES ON TELEOSTEAN OVA AND LARVAE. 23 



The Top-knots. (Zeugopterus.) 



I follow Petersen* in referring all three Top-knots known in the 

 Plymouth neighbourhood to the genus Zeugopterus. Under this heading, 

 then, we have to consider : — 



Zeugoptrrus norvegicus, Coll. (Scophthabnns norvegicns, Gthr.) 

 „ pundatiis {VA.) {Rhomhus pundatus, Gthr.) 



„ unimaculatus (Risso), Day. {Phrynorhomhus unimacu- 



latus, Gthr.) 



I have named them in order of the abundance of adults, so far as is 

 known, in the neighbourhood of Plymouth Sound. Zeugopterus norvcgi- 

 cus occurs fairly commonly on the Eame-Eddystone ground, and I 

 learn from fishermen that it has been taken in increased abundance of 

 late years. The other two species are more littoral, rock-haunting fish, 

 and therefore do not lend themselves to capture in a trawl to the 

 extent that Z. norvcgieus does. Z. pnnctatus is not infrequently taken 

 on the rocks between tide-marks, and sometimes finds its way into the 

 shrimp-trawl. Z. unimaculatus has not come into our collections in my 

 own experience at Plymouth, and I can only state that it lias been 

 known to occur here.f 



Holt (lid, p. 128) and Balfour Browne (2, p. 600) have taken pelagic 

 Zeugopterus eggs here in the spring months of 1897 and 1902, but 

 the observations have not yielded sufficient information to enable a 

 definite conclusion to be made as to their identity. I have been more 

 fortunate in obtaining a large number of eggs and in having at my 

 disposal the solution of the identity of one of the species, viz. Z. nor- 

 vegicus, which Ehrenbaum's work at Helgoland has rendered available 

 (5b, p. 210). 



Below I give a list of all the Zeugopterus eggs taken in my collec- 

 tions in 1909. In the majority of cases they were kept until the just- 

 hatched larva could be observed. It will be seen that they group 

 themselves into two classes, those in Column I having a diameter of 

 0"75-0 90 mm. and an oil-globule of 0'095-0'15 mm., while Column II 

 contains the larger eggs of 0'96-1'05 mm. diameter and 0"17-0"195 mm. 

 diameter of oil-globule. 



* Report of tlie Danish Biological Station, XII, 1902-3, p. 26. 



t A specimen of Z. unimacidafAis was, however, taken in the trawl o(f tln' Eddystone 

 in May, 1910, after this paper was in manuscript. 



