764 FUNNEL AND CAPITO-PEDAL CARTILAGE. 



of a median body with anterior and posterior cornua, the whole being shaped somewhat 

 like the letter H. It has frequently been designated by the same term which is applied 

 to the principal cartilage of the Dibranchs, namely, cephalic cartilage 1 , but this name 

 as applied to the cartilage of the Tetrabranchs is not only a misnomer but is positively 

 misleading, since the cephalic cartilage of the former is a cranial cartilage having essential 

 topographical relations with the central nervous system, and presenting definite fossae for 

 the reception of the cerebral, pedal and visceral ganglionic centres, and for the protection 

 of the otocysts, and foramina for the exits of nerves. 



In Nautilus the arrangement is more primitive in so far that the cartilage has essential 

 relations with the motor system generally (funnel and musculature), and merely exhibits 

 incidental contiguity with regard to the more ventrally situated parts of the nervous and' 

 sensory systems. It surrounds no part of the last-named systems, is not perforated by 

 any nerves, and is only traversed by one pair of blood-vessels, namely, the infundibular 

 arteries (PI. LXXXL). The principal fossae which it presents are related to parts of 

 the venous system, e.g. there is a deep fossa on each side nearly enclosed by cartilage, 

 for the passage of the infundibular vein, and a spacious median fossa for the anterior 

 reservoir of the vena cava. The deep fossa described by Owen for the lodgment of the 

 optic ganglia has no existence. 



The anterior cornua of the cartilage of Nautilus extend forwards into the substance 

 of the funnel 2 , which they help to keep open just as the posterior cornua of the skeleton 

 in Enteropneusta keep the mouth open ; the posterior cornua occupy the raphe which 

 separates the siphonopodiwm (funnel) from the cephalopodium; finally the body of the 

 skeleton lies at or near the angle of insertion of the funnel into the body-wall. 



The ventral surface of the body of the cartilage is produced into a median keel 

 which serves for the insertion of the transverse muscles at the base of the funnel, and 

 its upper surface is complicated by its special relation to the important venous sinus, 

 which collects the blood from the head and funnel and passes it on to the vena cava. 

 This sinus may conveniently be termed the endochondral sinus 3 . 



After what has been said it will be evident that the term " capito-pedal " introduced 

 by Professor Lankester 4 , describes the cartilage of Nautilus more appropriately than any 

 other available expression. Nevertheless the cartilage undoubtedly affords some support 

 and protection to the ganglionic complex and otocyst, especially the latter, since conjunctive 

 trabeculae traverse the space between the perineurium and the perichondrium, and also 

 between the periotic membrane and the latter, in fact the loculus in which the otocyst 

 lies is bounded posteriorly by the perichondrium and anteriorly by the brachial or pedal 

 perineurium. 



The direction of the long axis of the cartilaginous skeleton of Nautilus is probably 

 of importance in regard to the more general question of Cephalopod orientation, and it 



1 "Kopfknorpel" of Keferstein 1865 and Haller 1895. 

 '- "Within the crura of the funnel" (Owen). 



3 The endochondral sinus was described by Owen in the following words (memoir, p. 16): — "In the body 

 of the skeleton is excavated a large sinus, which receives the contents of the veins of the head and funnel, 

 and empties itself into the commencement of the great dorsal vein." The "great dorsal vein" of course 

 refers to the vena cava which is quite superficial and ventral, as Owen correctly states on p. 27 of his memoir. 



4 Art. " Mollusca," Encyc. Brit. 9th edit. 1883, Zool. Articles (1891), p. 143. 



