ROBSON— ON THE CEPHALOPODA 437 



posterior aorta upon the right side. Between the right and left efferent vessels and the 

 anterior aorta are found two small vessels which run to the surface of the renal capsules. 

 The genital artery leaves the heart in a median position in the antero-ventral region. The 

 auricles are small, simple and roughly triangular in shape. 

 The branchicB are shewn in fig. 2 &. ' 



Polypus. 



1. P. fontanianus (D'Orbigny). {Plate 66, fig. 5.) Amerique Meridionale, p. 28, 

 1835. 



One example, ?, Coetivy (1405). 



Distribution previously hnoivn : Peruvian and Patagonian regions. Indian Ocean. 



Originally regarded as a South American form, this species has recently been recorded 

 from the Indian Ocean {Joubin (12)). The enlargement of the proximal suckers of both 

 lateral arms, regarded by D'Orbigny as a character diagnostic of the species but now found 

 to be a sex-limited character found in other species, has been already discussed by Hoyle (5). 

 It may possibly serve a prehensile function similar to that discharged by the enlarged 

 thumb of male frogs. Insemination being effected among the Cephalopoda by means of 

 the hectocotylus it would appear unnecessary for the male to be supplied with prehensile 

 organs. Very little, however, is known of the actual process of sperm-transference and 

 coitus, and it may be possible that some form of amplexus takes place in some species of 

 Polypus in which the enlarged suckers seen in P. fontanianus and P. gay^dineri are used. 

 That amplexus may take place in some members of a genus and not in others is attested 

 by Boulenger's description (1) of fecundation in Batrachians, according to which amplexus 

 occurs in Molge aspera and M. montana but not in M. cristata and M. alpestris. 



The mandibles. The upper is erect and exhibits a well-pointed rostrum ; in the lower 

 the anterior laminse are provided with a marked posterior median angulation. 



In the radula the median tooth appears to exhibit three phases, one with lateral 

 cusps placed about half-way down from the apex of the median cusp, one with similar cusps 

 placed lower down and one with cusps in both positions. The third lateral tooth is stout, 

 recurved at the tip and its base is well developed. 



The anus is situated within a circular depression in the mantle cavity and is furnished 

 with two elongate valves. 



The heart is markedly asymmetrical. The genital artery leaves it towards the right 

 side, the anterior aorta well on the left with the root of the posterior aorta occupying the 

 opposite angle. Shortly after it leaves the ventricle the anterior aorta gives oft' a small 

 vessel which apparently runs to the stomach and intestine. 



The right auricle was found to be in an abnormal condition inasmuch as it was en- 

 larged to a size exceeding that of the ventricle itself. Dissection revealed the presence 

 in it of a mass of coagulated blood. The left auricle being, as is usual in the Cephalopoda, 

 of small size, one is forced to conclude that the distension of the right auricle is abnormal, 

 due either to pathological causes or to some temporary derangement of the circulation due 

 possibly to the circumstances of the animal's death. 



SECOND SERIES— ZOOLOGY, VOL. XVII. 56 



