Parxer.—Anatomy and Embryology of Seymnus lichia. 223 
« Family SPINACIDA. | 
« No membrana nictitans: two dorsal fins, no anal : mouth but slightly 
arched: a long deep straight oblique groove on each side of the mouth : 
spiracles present: gill openings narrow : pectoral fins not notched at their 
origin. 
« Genus Seymnus. 
« Two short dorsal fins without spine, the first at a considerable 
distance from the ventrals; dermal productions uniformly small; nostrils 
at extremity of snout; upper teeth small, pointed ; lower much larger, 
dilated, erect, triangular, not very numerous : spiracles wide.” 
Only species, S. lichia. 
1. External characters (fig. 15). 
The colour of the specimen is uniform dark brown and has been quite 
unaltered by the preparation of the skin for stuffing. 
The head is flattened and the snout very blunt, with the nostrils (na) 
near but not at its extremity; each nostril is guarded by a cutaneous flap 
on its inner side. The eyes (e) are large, and when fresh were remarkably 
beautiful, owing to the fact that the pupil was greatly dilated, allowing the 
silvery tapetum to be seen through the humours, producing a delicate 
greenish shimmer. There are 19 lower teeth. 
The body is markedly constricted a little behind the mouth, producing a 
sort of imperfect neck ; there is then a great increase of girth in the region 
of the shoulder-girdle, from the pectoral (pc) to the pelvic (pv) fins the 
circumference is tolerably uniform. 
As to the fins, the small size of the pectorals is noticeable, and the 
pelvies present a character, apparently not heretofore noticed, which appears 
to me of some morphological importance. This is a low ridge (l.r) extending 
forwards for some 6 or 8 inches from the anterior border of each pelvic fin, 
ascending somewhat as it goes. I think there can be no doubt that this is 
to be looked upon as a retention in the adult of the ridge which, as Balfour 
has shown, connects the pectoral and pelvic fins in the selachian embryo. 
On the lateral fin theory of the limbs, this ridge must therefore be considered 
as a rudimentary structure of considerable interest. 
Within the lips of the cloaca is a well-marked pair of abdominal pores 
(fig. 1, ab.p), which communicate with the abdominal cavity. The lateral 
line (fig. 15, 1.7) is very obvious. 
2. Alimentary organs. 
The stomach consists, as usual in Selachians, of a wide cardiac portion 
(fig. 1-8, ed. st) of but slightly greater diameter than the gullet, and of a 
small tubular recurrent pyloric portion (py. sé); the latter is unusually 
short, so that the anterior end of the intestine projects but slightly in front 
