Miscellaneous. 397 



opinion are Lowe and Clark. But most recent naturalists place 

 Truncatella among the Branchiferous Mollusca. The author has 

 obtained specimens oi Truncatella truncatula from the Gulf of Lyons, 

 and describes its general organization and especially its mode of 

 respiration. 



By carefully crushing the shell and then tearing to pieces the 

 anterior part of the animal the author displayed an elongated organ, 

 composed of from twelve to fifteen triangular lamellae covered with 

 long vibratile cilia. This organ, which is a true hranchia, is attached 

 to the roof of a large respiratory cavity observed at the dorsal sur- 

 face of the mollusk. It is placed transversely to the axis of the 

 body, and its lamellae can be moved by the animal simultaneously or 

 separately for the renewal of the surrounding water. The mollusk 

 can store up a certain quantity of water in its respiratory cavity, 

 which enables the animals to remain a long time out of the water. 



The author describes the principal points observed by him in the 

 anatomy of Truncatella. In front of the buccal bulb there is a long 

 proboscis, which may be employed to assist in locomotion, although 

 the foot is usually the sole organ of progression. In the buccal 

 bulb there are two horny jaws, and between them a very long 

 radula, of which the dental formula is 2, 1, 1, 1, 2. The stomach 

 is also furnished with horny pieces serving to complete the tritura- 

 tion of the food. The liver occupies the truncated extremity of the 

 shell (about the last two whorls) and is large ; it discharges itself 

 by a single duct, which opens into the intestine just behind the 

 stomach. 



The genital gland (male or female) is placed immediately in front 

 of the liver, to which it always adheres more or less. The excre- 

 tory duct (deferent canal or oviduct) runs along the right side of 

 the body, following the intestine, and opens into the respiratory 

 cavity near the anus ; in the male it terminates in a long, cylin- 

 drical, unarmed penis. More or less enveloping the intestine and 

 genital duct are various glands (the organ of Bojanus and prostate 

 or albumen -gland) ; but these could not be separated on account of 

 the small size of the animals. 



The nervous system consists of an oesophageal collar with two 

 voluminous centres placed above the oesophagus and almost joined 

 together, the cerebroid ganglia ; two inferior or pedal ganglia, nearly 

 as large as the preceding, to which they are attached by two con- 

 nexions on each side, and to each other by a long commissure ; and 

 four much smaller visceral ganglia, placed two and two at the sides 

 of the oesophagus and only united to the supra-cesophageal centres, 

 complete the collar. The visceral ganglia are united by two long 

 connexions with a fifth centre, the viscero-genital ganglion, which 

 is buried in the glandular mass surrounding the intestine. Besides 

 these nine centres there are the buccal ganglia, placed at the poste- 

 rior part of the bulb, below the origin of the oesophagus. The eyes 



Ann. & Mag. N. Hist. Ser. 5. Vol. xvi. 27 



