i8 



full account. Neither did I study the generative organs, nor the excretor)- apparatus. The organ 

 on the roof of the pallial cavity, which is probably the heart, has been mentioned already. 



Central nervous system: It differs very strikingly from that of Liviaciiia and is 

 almost identical, as regards the ganglia, with that of Cyrnbulia. I can only confirm Pelseneer's 

 discovery, after having studied the nervous system of Peraclis rissoides (PL I, fig. 14). The 

 pedal and cerebral ganglia are symmetrical, but instead of the asymmetrical visceral mass, 

 occurring in Limacina, there are "three ganglia, the two lateral of which are symmetrical and a 

 little smaller than the central one". With these words I agree entirely, only I found scarcely 

 any difference in size between the three visceral ganglia. 



Furthermore I have seen (i) a tentacular nerve issuing from the anterior part of the 

 cerebral ganglia (B), (2) the nerves to the fins and to the posterior lobe of the foot (Aj, 

 proceeding from the pedal ganglia, (3) a nerve proceeding from the right visceral ganglion (like 

 Pelseneer, I could not find one on the left), and (4) two visceral nerves from the median visceral 

 ganglion, one of them i.ssuing almost median, the other from the right side of the ganglion (A, 4, 5). 



The buccal ganglia, close to the oesophagus, are connected by a commissure. 



Geographical Distribution. 



Peraclis reticulata, first discovered by d'Orbigny ^), who considered it to be a Heteropod, 

 and several times found again by other investigators, seems to be very rare, though living over 

 a wide area. Living animals were caught in the Pacific Ocean (d'Orbigny, Souleyet, Boas) and 

 in the Mediterranean, (Pelseneer, Oberwimmer), while the occurrence of the species in the Atlantic 

 is somewhat doubtful, though the empty shells (without reticulation) have been recorded through 

 deep-sea dredgings -), even from the North-Atlantic. The Challenger Expedition found Peraclis 

 reticulata in the Atlantic only represented by deposit shells. 



Its occurrence in the East-Indian Archipelago was to be expected, as it has been found 

 in the Pacific Ocean (though in the eastern part) ^) by d'Orbigny, Boas (Chierchia Expedition) 

 and Pelseneer (Challenger Expedition). Pelagic animals being generally distributed over wide 

 areas, the variability in characters among the individuals of the same species is greater than 

 in organisms, strictly localised by their mode of life. An attentive examination of a number of 

 individuals from different stations will probably show some variations. 



Peraclis bispinosa *), recorded from the Atlantic by the Challenger Expedition and from 

 the Mediterranean"), is only known by its shell. The same is true of ""Spirialis diversa' ^) 

 Monterosato, found in the Atlantic. 



The two new species in the Siboga-material, Peraclis rissoides and Peraclis moluccensis. 



1) Voyage dans I'.^m^rique mevidiouale, vol. V, p. 174, figs. 32 — 35, 39. 



2) As to the synonymy, see I'ei.sknekk, Chall. Rep. LXV, p. 32. 



3) SoULEVET (Voyage de la Bonite, vol. II, p. 221) has not noted a distinct locality; he s.ays only: "dans I'Ocean Pacifique". 



4) Pelseneer, Chall. Rep., I.XV, p. 36, pi. I, figs. 9 — 10. 



5) Oberwimmer, in Denkschr. K. Akad. Wiss. Wien, Bd. LXV, p. 589. 



6) Nuova levista etc., in Atti Acad. sc. lett. ed arti, vol. V, p. 50. This species was lefened by Pelseneer to Peraclis 

 bispinosa (though with some doubt, as the description of DE Monteros.mo is insufficient). It seems, however, a well defined species 

 of Peraclis (though with deep umbilicus!), according to Locaed, Expeditions scient. Travailleur et Talisman, Moll, test., vol. II, 

 p. 29, pi. I, figs. 4—6. 



