1900.] THE SKULL OF A YOUXa RIBBOX-FISU. 555 



Summary. 



From these notes, it will he evident that nearly ever}' hone 

 in the skull of this small Eihhon-fish differs, to a greater or less 

 extent, either in form or proportions, from the corresponding 

 hone of the Great E-ihhon-fish. 



The specimen was undouhtedly a young one — a fact which is 

 shown not only hy the amount of cartilage in tlie skull, hut also 

 hy the condition of the ovary, in winch aU the eggs were small. 

 There are, therefore, two possible explanations of the differences : 

 (1; that the fish was the young of a known species, probably 

 it. glesne, which is the common species ; or (2) tliat the fish belongs 

 to a different species. If the specimen is the young of i?. glesne, 

 the changes which it must undergo before becoming adult must 

 be far-reaching, especially in the skull. For example, the 

 posterior pai-t of the parasphenoid must gr-ow backwards with 

 gi-eat rapidity, while the rest of the bone continues its ordinary 

 growth. In order' that the parietad could assume the position 

 occupied by that bone in R. glesne, it would have to grow 

 enormously antero-posteriorly ; but, before it could do so, the 

 backwardly directed process of the frontal, which lies between 

 the parietal and the posterior dorsal groove, would have to 

 disappear, Tlie maxilla, too, would have to change its shape 



entirely. Now the maxilla is a particularly well-ossified bone 



one of the best ossified in the skull — and so least likely to undergo 

 f ui'ther developmental change. Such great changes as are here 

 indicated would hardly have been expected after the animal had 

 attained more than its half adult length. 



Conclusion. 

 Taking all the facts into consideration, it seems more than 

 probable that the so-called R. parkp/ri is but the young stage of 

 R. glesne. 



BiBLIOGEAPHY. 



1. Bexhaii. — "An apparently new ^])ecieii oi Regalecus {R. par- 



Jceri)." Trans. X.Z. Inst. xxx\t.. jj. 198. 



2. Yox Haast. — " Notes on the Regalecus x^f^ificus." Trans. 



X.Z. Inst. X. p. 246. 



3. Parker. — " On a Specimen of the Great Ribbon- fish [R. argen- 



teasy Trans. N.Z. In.st. xvi. p. 284. 



4. Parker. — " On a Specimen of Regalecus recently Stranded in 



Otago Harbour." Trans. N.Z. Inst. xx. p. 20. 



5. Forbes. — " On a species of Regalecus caught in Okain's Bay." 



Trans. N.Z. Inst. xxiv. p. 192. 



6. GooDE (i; Beax. — ' Oceanic Ichthyology,' p. 480. 



7. Drew. — " Notes on Regalecus sp." Trans. X.Z. Inst. xxx. p. 253. 



8. Clarke. — " Notes on the Occurrence of R. argenteus on the 



Taranaki Coast." Trans. N.Z. Inst. xxx. p. 254. 



9. Parker. — " On the Skeleton of R. argenteus." Trans. Zool. 



Soc. xii. p. 5. 



