'ril01!Nl!ACK. 



1 1 07 



the Mediterranean and the Black Sea (Pallas), and 

 it has been found off Madeira (Guntiiek). 



In the island-belt of BohusUln Thornbaeks both 

 young and old are taken all the jear round. During 

 winter, however, they are less common, and the fisher- 

 men state that at this season the Thornback rejjairs to 

 deep water, in spring and summer it is very plentiful 

 off the coast, where it seems to prefer water of a mo- 

 derate depth" and with a sandy bottom. It lives almost 

 invariably at the bottom and extremely seldom ascends 

 to a higher level. Its food consists of small fishes, 

 crustaceans — crabs, lobsters, shrimps, etc. — mollusks, 

 Annelids, Echinoderms, and Acfinm''. 



Throughout the summer the females contain deve- 

 loped ova; but according to Fries only one egg is laid 

 at a time, and the period of oviposition for each female 

 must consequently l)e of long duration. Fries obsei'ved 

 that, on opening old females in summer-time, the egg- 

 clusters in the ovaries are found to be considerably 

 tumid, the several eggs showing different grades of 

 development, from the size of a pea to that of a plum. 

 In tlie two oviducts however — each of them dilated 

 below into a uterine organ — he never found more than 

 a single egg, and this alreadj- invested with the sin- 

 gular corneous shell. When one of the uteri contained 

 an Qgg, the other was emptj-. The ovum is of the form 

 normal among the Rays, rectangular, with the four 

 corners prolongated in its longitudinal direction, and 

 according t<i Malm' is 55 — 57 ram. long and 40 mm. 

 broad, liut including the tilaments at the corners 110 

 — 115 mm. long. Fries once found a female Thorn- 

 back with a half expelled egg in the cloaca. On ex- 

 amination the ])rotmding end of the egg proved to be 



(:H)en, tlie larva hM\ing alreach' left the sliell. lie dis- 

 sected the specimen, and saw that the Icift uterus was 

 empty, })ut tlial in the rigiit there lay a recently de- 

 scended o\ uni, the sliell of whicli was still very soft. 

 In this case it was consequently evident that the em- 

 bryo had freed itself from tlie egg immediately on the 

 expulsion of the latter. Malm, on the other hand, 

 never found a viable foetus, scarcely a distinct embiyo, 

 in newly de])osited ova, whence he inferred that the 

 development of the (nid)ryo does not commence until 

 the egg is laid'. Tlie process of develoj)ment may thus 

 vary in its acceleration; but l)y far the greater number 

 of the eggs found after liberation are empty. During 

 their early life, according to Khoyer, the fry keep to 

 the shallows of shelving coasts. 



The Thornback is taken on long-lines and in Floun- 

 der-nets, less frequently in the seine. As an article 

 of food it enjoys a good reputation in Great Britain 

 and Ireland, especially in the latter country'; but 

 in the island-belt of BohusUln, according to Ekstrom, 

 it is regarded as one of the poorest fishes. It is hardly 

 ever eaten fresh there, at all events by the islanders, 

 who instead dry the flesh in the open air on flakes 

 {gdUar) or platforms, constructed in elevated situations. 

 After drying it is sold to tlie peasants of the agricul- 

 tural districts, who use it as a substitute for lutfisk^ at 

 their Christmas festivities, and consider it good eating. 



Besides knaggroclm (Spin}' Hay) this species bears 

 in the island-belt of Bohusliin the names oi piggrocka, 

 as adult, and rockhok and pcnik, while young. On the 

 coast of Scania it shares with the following species the 

 name of torr-horr, according to Lilljeborg a corruption 

 of the Danish Tavhe. (Fries, Ekstrom, Smitt.) 



" According to Malm the full-grown Thornback is only seldom found in less than 14 f.atlioiiis of water. 



* See Olsson, Fiskavnes foda, Lunds Univ. Arsskr., torn. VIII, 1871. 



■■ Ofrere. Vet. .\kad. Forh. 187G, No. 3, pp. 94, 95. 



" Ghijs, Boh. Fauna, p. 607. 



' See D.4Y, 1. c, p. 345. 



•^ Dried Cod etc. soaked in Ij-e before cookins. Tliis is still a sLipl ■ course in Sweden at Clirislmas and on oilier feast-days. Tr.. 



