of the Fishery Board for Scotland. 75 



One of the specimens at St. Andrews was considerably the shorter, and 

 will be referred to in this memoir as specimen A. From specimen B, the 

 larger, the yolk had been removed ; this specimen was accordingly used for 

 dissection, while the other was preserved for the Museum. The embryo 

 examined at York will be referred to as specimen 0. 



The measurements in the appended table are in millimetres. Specimen 

 C is placed between A and B in the table, since it was intermediate in size. 



Region measured. 

 Tip of snout to base of caudal fin, ... 



Caudid fin (round the curve) \ JJ^^P^'' !°I'^'- 

 ^ ' [ Lower lobe,... 



Tip of suout to anterior extremity of eye, 



Width of eye socket, ... 



Eye to nostril, ... 



Eye to mouth, vertically. 



Tip of snout to upper lip, 



Width of head, eye to eye 



Posterior extremity of lips to first gill slit, ... 



Tip of snout to anterior end of 1st dorsal fin. 



Length of 1st dorsal at base, ... 



Vertical height of 1st dorsal, ... 



Tip of snout to anterior end of 2nd dorsal fin, 



Length of 2nd dorsal at base, 



Vertical height of 2nd dorsal, 



Base of pectoral fin, ... 



Length of pectoral. 



Posterior of pectoral base to anterior of pelvic, 



Base of pelvic, ... 



Length of pelvic. 



Base of aual fin. 



Length of anal, 



Length of cloaca, 



Anterior of cloaca to base of caudal, ... 



Anterior of lower lip to chin pit. 



Chin pit to anterior end of yolk sac, 



Girth of yolk-sac at contact with body. 



Maximum girth of yolk-sac, ... 



Girth of yolk-sac from flank to flank (not 



allowing for body width), ... ... 360 385 



External Appearance. 



The young porbeagles closely resemble the adult in external features, 

 except for the presence of the bulky yolk-sac (PI. IX., fig. 1). The cylin- 

 drical body lies in a somewhat curved posture over the large ovoid yolk-sac, 

 with which it is in contact between the pectoral and pelvic fins for a 

 distance of 100 mm. The dorsal aspect of the head is flattened. The snout 

 is much blunter than that of the adult. The nasal apertures are connected 

 by a furrow. There is a chin pit on the ventral aspect of the head, situated 

 a few centimetres behind the lower lip ; in specimen C there was no distinct 

 pit, the under surface in the branchial region forming a shallow concavity, 

 rounded in front, to which the anterior projection of the yolk-sac is closely 

 applied. The inter-nasal furrow and chin pit are embryonic characters, and 

 are not found in the adult. The eyes and mouth are well developed, the 

 latter containing a few small teeth. The latter do not show the two lateral 

 cusps said to be present in the adult. 



F 



