30 Moll . 
mollusga; 
yet’s account of its anatomy. The genus is chiastoneurous ; the triangu-! 
lar cerebral ganglia are placed antero-laterally on the pharyngeal sac, 
and united by a long sub-oesophageal commissure, and give off the thick 
proboscidial nerves as well as the cerebro-pedal and cerebro-commissural 
connectives. The pedal and commissural ganglia form a quadrilobato 
infra-buccal mass, while a branch from the proboscidian nerve passing 
between the oesophagus and the buccal mass enters the horse-shoe- shaped 
stomatogastric ganglionic mass. The nervous system of the Neritidce and 
Navicellce resembles closely that of Turbo ; but it is noteworthy that, so 
far as investigations have yet gone, it does not seem to be chiastoneurous ; 
Bouvier (6). 
Concholepas sp. is externally parasitic on LincTcid multiformis , from 
Ceylon : it occurs on the lower surface of the arm, attached by a number 
of elevations, which penetrate the cutis. The centre -of this surface is 
occupied by the pharynx, which acts as a proboscis, and has a pumping 
action ; there is no radula. “ The true foot is a small semi-lunar fold on 
the hinder surface a similar anterior fold being the remnant of the 
velum. There are salivary glands and one gill ; the adult shell is 1 
cm. long, and has a general resemblance to Ancylus ; Sarasin. 
Stylina sp. forms conical swellings on the arm of Linckia multiformis , 
the apex of the shell, which is 1 cm. long, and has 8 whorls, projecting 
from an aperture. Thero is a false mantle, acting as a respiratory pump, 
and a muscular proboscis, which may extend 1*5 cm. Pharynx, radula, 
and operculum are absent ; eyes and otocysts present ; the sexes are 
separate ; Sarasin. 
The body of Pterotrachea may be regarded as a tube of muscular and 
gelatinous material, the latter enclosing numerous large cells with large 
nuclei ; in the post-anal tail the muscles are in four bands, and the large 
round cells are replaced by stellate ones ; the fin consists of two muscu- 
lar plates. There are four groups of ganglia : (1) three pairs of cerebral ; 
(*2) one pair of pharyngeal ; (8) one pair of pedal ; (4) two unpaired 
visceral ganglia. The “ ciliated organ ” consists of a nervous band, 
derived from the visceral ganglion, with a fibrous centre and peripheral 
ganglion cells, and an epithelial portion exhibiting a median mass of 
large stratified cells, with a depression where the nerves enter and a 
lateral elevation of long ciliated cells. A muscular cul-de-sac is formed 
at the root of the tail, and below it is the pericardium, which is quite 
distinct from the perienteric cavity. The branchiae round the ciliated 
organ are desci ibed ; the oesophagus is much elongated, and the intestine 
and liver reduced. An aberrant Heteropod [? allied to Carinaria ] is 
described ; Warlomont.' 
Bergh (4) expresses the opinion that Phcenicurus is merely a papilla of 
Tethys. Lacaze-Duthiers (1) replies, stating that Dujardin had pointed 
out the resemblance of such papillae to the true Phcenicurus , distinguishing 
between hepatic caeca and the dendrocoelous intestine of Phcenicurus, and 
asking of what use to Tethys can be appendages which fall off so easily. 
Spengel complains that Lacaze-Duthiers has neglected the whole pre- 
vious literature on Phcenicurus , and confirms Bergh ’s view that these 
organisms are merely papillae of Tethys ; see also Mobius (2). 
