REPORT OjST THE PTEROPODA. 
11 
describes tbe visceral ganglia in “ Spinalis ” australis as like those of Cavolinia, that is 
as forming a single mass. I have had the opportunity of studying this form as well as 
Limacina helicina, and can state that in it, as well as in Limacina lesueuri , Limacina 
trochiformis, and Limacina inflcita, the ganglia of the visceral commissure are disposed 
in the same asymmetrical fashion. The distribution of the nerves is also certainly 
identical, but it is difficult to distinguish this in the case of such small animals. 
The enteric or stomato-gastric nervous system includes a pair of buccal ganglia, 
united by a thick and rather long commissure. These ganglia are placed in contact with 
the oesophagus below the pedal ganglia ; each of them is joined to the corresponding 
cerebral ganglion by a thin connective. They give off anteriorly the nerves to the 
buccal mass, and posteriorly two filaments which pass along the oesophagus to the 
stomach, where they ramify and anastomose, so as to form a plexus whose appearance 
varies a little in different individuals. Some ganglionic thickenings are observed in 
the plexus. 
2. Peraclis. 
The Head is quite differently shaped from that of Limacina ; it is quite distinct, as 
I have already had occasion to point out in the systematic part of this Report ; it has 
the form of a short proboscis issuing from the dorsal margin of the fin (PI. I. fig. 9, a), 
the two lips uniting dorsally and ventrally ; the two tentacles are symmetrical, and have 
no sheath. It is this proboscis which in Costa’s figure 1 might easily be taken for the 
ventral lobe of the foot, which would be notched in the middle of its free margin. 
The Foot . — The fins have no tentaculiform lobe ; the ventral lobe of the foot is 
not notched in the middle of its free margin, but is broader at the base than at this 
margin. 
The Mantle has on its right margin, a little ventrally, an appendage in the form of a 
triangular lobe, analogous to the balancer of Limacina. The dorsal pallial gland 
(shield) is shorter than in Limacina. It is not homogeneous, as in the case of this 
latter, which resembles that of Clio (subgenus Creseis), but presents alternating transverse 
bands (PI. I. fig. 10). It is asymmetrical like that of Limacina. 
The Digestive Tract agrees with that of Limacina, both in the relative position of its 
constituent parts and in their shape. As in Limacina there are two lateral jaws, two 
little salivary glands, and five large masticatory gastric plates, of which four are sym- 
metrical, and the fifth triangular, posterior, and dorsal. Furthermore, as in Limacina, 
the bile-duct opens into the left of the digestive tract, and the flexure of the intestine 
is dorsal and to the right. 
The visceral anatomy of Peraclis is otherwise very similar to that of Limacina, and 
1 Illustrazione della Spirialis recurvirostra, Ann. Mus. Zool. R. Univ. di Napoli, anno iv. pi. iv. fig. 12. 
