SCAll. 



87 



l)elo\v the isthums to tliat on the otlitT side. There 

 ai-e 7 curved, bi'anchiostegal raj^s on eaoli side of the 

 body. Tlie body is covered Avith small, (hin, ovnl scales 

 of dirt'erent sizes, tiiid only the tins, the c-iiidal fin ex- 

 cepted, the snout and the h)\ver jaw are naked. The 

 smaller scales of the body grow even Ijetween the pla- 

 tes of tlie lateral line, especially in the front part. The 

 lateral line begins at the upper margin of the gill- 

 oj)ening, then runs in an almost imperceptible upward 

 curve to a point vertically above the vent, where it 

 forms a downward curve, and is then continued in a 

 straight line to the base of the caudal tin. It is com- 

 pletely covered by about 75 transverse plates. Of these 

 plates the anterior ones, from the beginning of the line 

 to its curve at the end of the pectoral fins, are smooth ; 

 but from this point they are furnished Avith a high, sharp 

 keel, Avhich ends behind in a strong spine. The height 

 of tlie keel gradually increases and hence the tail is 

 twice as broad as high at the end of the dorsal fin. The 

 number of spinous plates is from 35 to 38. These keels 

 may be traced even in the skeleton by the hook on 

 each side of the last caudal vertebra. The vent is 

 about half-waj' betAveen the tip of the snout and the 

 middle of the base of the caudal tin, or a little in 

 front of (sometimes at) the middle of the body". 



The anterior dorsal fin begins Avith a spine point- 

 ing forAvard and often covered by the skin, vertically 

 above the insertion of the ventral fins, and ends above 

 the vent. It is short and high, Avith 8 unarticulated, 

 but weak, rays. The posterior dorsal fin is long, ends 

 above the end of the anal fin and generally contains 

 from 30 to 33 rays. Tiie first of these is unarticulated 

 and half as long as the second, Avhicli, like all the 

 others, is branched and articulated. The pectoral fins 

 are narroAv, falciform and equal in length to the head. 

 They each contain 19 or 20 rays, the tAvo uppermost 

 undiA-ided and the top one of all unarticulated, the 

 others branched oftener and oftener to the loAver side 

 of tlie fin. The ventral fins are long and pointed, ex- 

 tending almost to the vent. In form the anal fin is 

 like the second dorsal. It generally contains 28 or 29 

 rays, the first of Avhich is unarticulated. In front of 

 this fin is another smaller one, Avith only tAvo, small, 

 spinous rays, Avhich are joined by a membrane. Tlie 

 caudal fin is crescent-shaped, Avith 18 or 19 long rays, 



the two outer ones being undivided; there are also 4 

 or 5 smaller (rudimentary) rays at the toj) and bottom 

 of the base. 



The colour of tlie back is dark olive-green Avith 

 lighter, Avavy, transverse Ijands. The head and the 

 sides beloAv the lateral line silver Avith a dash of orange, 

 like mother-of-pearl. The iris silver- Avhite, the ])Upil 

 dark blue. The intei'i(jr of the mouth black like the 

 inner side of the branchiostegal membrane, Avhich is 

 edged Avith silver. A large black spot at the upper 

 margin of the gill-opening. The anterior dorsal fin 

 transparent, the posterior dark gray, as is also the 

 caudal: tlie other fins Avhite. 



The interior of the abdominal cavity is dark in 

 colour, the liver pale red, large and bilobate, and the 

 spleen large and triangular. The kidneys are black 

 and of average size. Tlie intestinal canal bends tAvice. 

 The stomach is large and there are a large number 

 of pyloric appendages (from 12 to 20, according to 

 Gunther). The ovaries are large, but the eggs small. 



The food of the Scad consists of small fry and 

 crustaceans. The most usual contents of the stomach 

 are young Herrings, Sprats, or Sand-launces. It occurs 

 in the Cattegat all along the coast of BohuslRn and is 

 by no means rare, but is ahvays taken singly. Ekstroji 

 never found it in shoals, as it lives in other places, 

 and could never hear of its being so found. According 

 to NiLSSON, it has, in addition to the name given here, 

 those of tar/gsUl and, oft Kullen, staggsiU and staksiW'. 

 Malm says that in Bohusliin it is called piggmakrel 

 (Picked Mackerel) and skrej, Avhile CederstrOm also 

 gives the name of sUfverfisk (Silverfish). 



The Scads Avhich are caught by Avhiffing (Sav. rann- 

 dorj — running-line) during the Mackerel-fishery in 

 Bohuslan, at the beginning of June, have ripe roe in 

 the ovaries. It may therefore be assumed that the 

 spaAvning-season occurs in this month, though no place 

 is knoAvn Avhere this fish spaAvns. Most jirobably it 

 does so out at sea. That it really does spaAvn in the 

 Cattegat, is proved by the occurrence there of the fry, in 

 companv with the large jelly-fish {Cganea capUlata) so 

 common there, of Avhich it seems to be a sort of para- 

 site'. The fry stay under the body of the jelly-fish, 

 among its ovaries, and seem to feed exclusivelj- on its 

 eggs. This most remarkable habit Avas first observed by 



" In Todd's figure (Brown-Goode, 1. c.) the vent is situated considerably in front of the middle of the body. 

 '' All three names are about equivalent to 'Spiny-Herring'. Tr. 

 " ilALM (1. c.) also found the fry in Rhizostouia Aldrovandi. 



