140 Royal Society :— 



in connexion with which we notice a pair of lateral horny jaws arti- 

 culated with each other superiorly, and beset with very minute and 

 sharp-pointed teeth along the cutting edge, altogether much resem- 

 bling those of Glaucus, and a lingual ribbon gradually increasing in 

 diameter from before backwards, and supporting a pavement of long, 

 conical, flattened and gracefully curved teeth with fine denticula- 

 tions at the base. The central series of plates being symmetrical, 

 the large tooth in each takes up a middle position, but in the lateral 

 plates it inclines to the inner side. In some examples I have ob- 

 served certain lobulated bodies lying in contact with the buccal 

 mass, and which I am disposed to I'egard as salivary glands. The 

 oesophagus is short, and suddenly expands into a moderately large 

 stomach ; and the latter, having received the biliary ducts near its 

 posterior extremity, is continued into the rectum, which passes 

 directly backwards some little distance, and ends in the anus, on the 

 right side of the bod}', at the union of its posterior and middle thirds. 

 The liver in PhyUirrhoii consists of four elongated, tubular, and sac- 

 culated portions or lobes, disposed along the borders of the body, 

 two lying above and two below the alimentary canal. Each of the 

 superior hepatic glands opens bj' a distinct duct into the supero- 

 posterior part of the stomach, while the ducts of the inferior ones 

 unite to form a common tube joining it at its infero-posterior part. 

 The opposite or cacal extremities of the two anterior hepatic lobes 

 end in the neighbourhood of the head, while those of the others 

 extend to within a short distance of the tail. The secreting cells of 

 these organs are of a rounded or polyhedral form, containing, be- 

 sides the nucleus, a reddish-brown pigment and fatty globules. 



PhyUirrhoii possesses a simple systemic heart, consisting of a single 

 auricle and ventricle. This organ lies upon the stomach, between 

 the ducts of the two su])erior biliary glands ; and a large vessel or 

 sinus, with many circular constrictions in its walls, may be traced 

 towards the auricle, bringing back the aerated blood from the hinder 

 extremity of the body. Tliere are no visible respiratory organs, but 

 it is probable that the cutaneous surface permits of the necessary 

 exposure of the blood to the air contained in the surrounding 

 medium. 



The nervous system is well developed. The supra- and subceso- 

 phageal ganglia, with their commissural chords, form a close ring 

 round the gullet immediately behind the buccal mass. The audi- 

 tory sacs, which are filled with vibratory otokonia, appear to lie be- 

 tween both sets of ganglia, and the rudimentary visual organs, con- 

 sisting each of a simple cell containing a refracting globule imbedded 

 in ijlack pigment, are also in contact with the nervous matter. Be- 

 sides the actual distribution of the nerves given eft" from the cephalic 

 ganglia, I noticed nodules of neurine lying at the base of the tenta- 

 cula, communicating by commissural threads, and sending off each 

 a principal nerve to the corresponding tentacle. The ganglion- 

 globules were lined with a reddish-coloured pigment, deposited 

 round the vesicular nuclei, and when twigs are given off from the 

 smaller nerves, both the homogeneous neurilemma and the contained 



