570 SIR CHARLES ELIOT. 



round the club much as in Tritunia. The mantle overhangs the head : there are no anterior 

 tentacles, but the head is broad and crescent-shaped with produced ends. The mouth is 

 ventral : the front of the foot square, without tentacular prolongations. The jaws are large 

 and not denticulate. The middle tooth of the radula has a central cusp with 7 — 8 denticles 

 on either side, and the laterals are denticulate on the inner margin. The ganglia of the 

 central nervous system are distinct. 



This genus is recorded from the Indian Ocean (A. and H.) and Zanzibar, where I 

 have captured many specimens. The external characters of the animal vary somewhat with 

 the size, that is presumably with age. The smaller specimens are as described above. The 

 larger have many more cerata, and the papillae in the centre of the back (which apparently 

 do not contain hepatic ramifications) pass up between the rhinophores, forming a sort of 

 rudimentary crest. They have also a white patch between the rhinophores, which is absent in 

 the smaller individuals. When kept in captivity Madrella pours forth a peculiar ferruginous 

 secretion, which discolours the water round. It appears to proceed from the whole surface 

 of the body, not from any one gland, and is of much the same colour as the skin, so that 

 the creature looks as if it were dissolving. 



There are four more families of the Cladohepatica which are sometimes classed together 

 as the tribe Elysioidea (Pelseneer) and sometimes united with Oxynoe and Lohiger as the 

 Ascoglossa (Bergh) or Saccoglossa (v. Jhering). They are (1) Hermaeidae, much like 

 Aeolids externally but without oral tentacles. (2) Phyllobranchidae, with peculiar flat 

 leaf-like cerata. (3) Elysiadae (including Placohranchus), with no cerata, but lateral ex- 

 pansions or wings. (4) Limapontiadae, small forms with no cerata, wings or appendages, 

 and often with neither tentacles nor rhinophores. All these families have a ramified liver 

 and also the following anatomical characters. (1) There are no jaws. The radula consists 

 of a single series of teeth, each fitting into the next. The front teeth instead of becoming 

 worn away and destroyed fall into a peculiar pouch in which they are preserved. This 

 form of radula may be conveniently termed " ascoglossan." (2) In the nervous system the 

 cerebral and pleural ganglia are fused, the pedal ganglia are approximated and the visceral 

 commissure bears three ganglia (but in Limapontia only two). (3) The reproductive organs, 

 though imperfectly understood, are extremely complicated, provided with accessory glands 

 and ramified throughout the body. The male and female orifices are far apart, and there 

 are generally two of the latter. 



Fam. Hermaeidae'. 



The Hermaeidae closely resemble Aeolids and can hardly be distinguished by any ex- 

 ternal character except that the oral tentacles are not developed. Stiliger Mariae was 

 described by its discoverers, Meyer and Mobius, as an Embletonia. Internally, the family 

 is distinguished from the Aeolids by the following characters: (1) Jaws are absent and the 

 radula is ascoglossan, (2) the nervous system is formed of seven ganglia, (3) the hepatic 

 system is somewhat as in Fiona, there being no posterior hepatic trunk: the lateral branches 

 are often much ramified in the cerata and dorsal integuments. The vent as a rule is dorsal 

 and anterior. (4) The genital apparatus is much complicated by the presence of accessory 



> Alder and Hancock, Brit. Nudibr. MoUusca. Bergh, Golfe de Marseille, 1888. Pelseneer, Recherches sur divers 

 Beitr. zur Kennt. der Aeolidiaden, iv., v. and vin. Id. S. R. Opisthobranches, 1893. 

 Heft XVI. Vayssiere, Recherches sur les Moll. Opisth. dit 



