78 Dr. Morch on the Homology of 



Clione its two halves can cover the arms entirely, like a hood 

 (see Eschricht's ^ Anatomic^), and resemble the "crates auricu- 

 laires " and " paupieres inferieures " of D'Orbigny, above men- 

 tioned. 



3. The post-tentacular veil is only found in the larval state of 

 Rissoa, Loven (Ofversigt, 1847), and in the genera Chiropteron 

 of Sars* and Macgillivrayia of Macdonald. 



In analogy with the names of the foot given by Prof. Huxley, 

 these three kinds of velum may be called Prohistion, Mesohistion, 

 and Metahistion. 



That the short arms of Cephalopoda cannot be considered 

 the homologue of the foot, is evident from the circumstance that 

 the same kind of arms is found in the Pteropoda Gymnosomata 

 simultaneously with an undoubted foot. Prof, Loven first 

 showed that the funnel must be the foot of Gasteropoda, and he 

 suggests that the interior valvula of most Decapods and of 

 Nautilusf corresponds to the solea pedis of Gasteropoda — a 

 proposition which, I believe, is correct. The funnel would thus 

 correspond to the epipodium in the Gymnosomata; its dorsal 

 wings, attached to the neck of nearly all Decapod Cephalopoda, 

 are provided with three cartilages which may be compared to 

 a tripartite operculum J, thus proving that the lobus operculi- 

 gerus of Loven § is a part of the epipodial line (Huxley), and not 

 of the true foot (solea). 



Pedipes afra, as represented by Adanson (Hist. Nat. du S^n^- 

 gal, tab. 1) and by Lowe (Zool. Journ. vol. v. pi. 13. f. 8, 9), is 

 the only example of a foot divided into the propodium, meso- 

 podium, and metapodium of Prof. Huxley. 



EXPLANATION OF PLATE VL 



Fig. 1. Pneumodermon : intestinal channel, with the labial suckers, sali- 

 vary glands, stomach, rectum, and anus. The cheek-pouches 

 are united at their ends by a muscular band. 



Fig, lb. The oesophagus opened, to show the entrance of the cheek-pouches, 

 with the prehensile hooks in the centre, on both sides of the 

 radula. 



* Chiropteron semilunare, Sars (Beskrivelser og Jagttagelser 1835, 1. 14. 

 f. 38), is probably the larva of Aporrhais. 



t R. Owen, ' On the Pearly Nautilus,' t. 3. f. 2 e. 



X The middle cartilage is articulated to the inside of the front of the 

 shield or dorsal plate, and the two lateral cartilages to similarly excavated 

 plates in the inner margins of the mantle. 



§ The dorsal part of the metapodium (Huxley, " On the Morphology 

 of Cephalous MoUusca," Phil. Trans. 1863, p. 29). 



