248 
PLAGIOSTOMI. 
Mr. Templeton noted this species as taken “ occasionally.” The spe- 
cies has not come under my notice in the N., nor can Dr. Ball attest to 
its being seen by him on the Irish coast, but some ova sent to the Belfast 
Museum, in Dec., 1843, seemed to me to belong to this sp., and the fol- 
lowing paper drawn up on them was published by me in the Annals Nat. 
Hist, in 1844 : — 
“ On Ova believed to be those of the Large-spotted Dog-fish, Scyllium 
Catulus, Linn. (Sp.) 
u About the middle of December last there were sent to the Belfast Museum 
two plants of the tangle ( Laminaria digitata ), dredged together off Killinchy, 
Strangford Lough, from a depth of between two and three fathoms, and having 
many large and remarkable ova attached to them by tendrils, like those on the 
well-known ‘ purses, 5 as they are called, of the common dog-fish ( Scyllium Ca- 
nicula), though they evidently belonged to a different species. They were new to 
me and interesting in several respects. To the one plant of tangle -s^bre attached 
fourteen, to the other twelve, of these ova ; of the fourteen, six were very old, six 
of ‘ middle age,’ and two quite fresh — of the twelve attached to the other plant, four 
were very old, four of middle age, and four quite fresh. Those called fresh had 
the ‘ white and yolk, 55 as in a newly-laid hen’s egg ; from those termed of middle 
age the young fish had probably long since escaped ; none remained to bear 
testimony to its species. The age of the different ova was denoted, not only by 
their own appearance, but by that of the mollusca, zoophytes, &c., parasitical upon 
them ; — on the oldest were Anomice an inch in diameter ; Discopora hispida, 
Tubularia ramosa, Cellularia reptans, all full-grown ; and on them, and those 
of middle age, were Lepralice (Johnston) of various species, Nulliporce, and 
masses of the ova of Buccinum undatum. 
“ The number of ova of different ages suggested certain points of inquiry. Their 
deposition at three different periods of time on the same plant led to the sug- 
gestion that the fish may, like certain birds, as the different species of Hirun- 
dines, for example, return time after time to the same spot to deposit its eggs. 
We can indeed only infer that the same individual has deposited ova on the dif- 
ferent occasions, but the probability is in favour of such inference. That the 
salmon ( Salmo Salar ) returns to its native river — if not to the same ‘bed 5 — to 
spawn, we have a notable example in the North of Ireland, where, from the cir- 
cumstance of the fish of the adjacent rivers Bann and Bush being distinguished 
from each other by certain peculiarities, those of every age from each river in 
returning to the fresh water from the sea are known always to seek the ascent 
of their native stream. 
“ Being unable to find any ova described like those under consideration, I 
made a sketch of one and submitted it to my friend Mr. Yarrell for his opinion, 
together with several queries, remarking at the same time, that as ‘ the ova are 
evidently generically related to those of 8. Canicula, the first impression is, that 
they are those of the most nearly allied species, Scyllium Catidus, especially as 
we find those of the next nearest ally, at least among British species — Squalus 
annulatus, Nils. ( Pristiurus melanostomus, Bonap.) — to be of a different form ; 
but that, if they belong to & Catulus , which is said not much to exceed S. Ca- 
nicula in size, it will be singular that the ova should so greatly exceed those be- 
longing to that species as to be double their size, and, in consequence of their 
much greater strength, about four times their weight. The transverse markings 
represented in the drawing denote plaits, which give to the exterior a handsome 
appearance ; but they are not of specific value, the surface of some ova being 
quite smooth, of others partially or wholly plaited. 5 It was added — ‘ Is it known 
how often the Scyllia deposit their ova ? how many are deposited at one time ? 
how long after deposition the young fish bursts its prison ? 5 In the event of 
Mr. Yarrell’s not knowing the ovum (which proved to be new to him likewise), 
he was requested to send the drawing, &c., for Mr. Couch’s opinion. With re- 
spect to 8. Canicula Mr. Yarrell remarked, — 
“ I never remember to have observed more than one egg in each oviduct ready 
