CLASS II. GASTEROPODA: ORDER 3. HETEROPODA. 517 



THE APLYSIAD^. 



These animals, called Sca-Hares, are slug-like in form, the head distinct and furnished with 

 tentacles and eyes ; the shell is absent or rudimentary. They are found among sea-weed, from 

 which they derive a great part of their subsistence; they feed also on animal substances. 

 When alarmed or molested, they emit a violet or reddish fluid from the mantles, long supposed 

 to be poisonous, but now known to be harmless. Forty species are found in the Atlantic, Medi- 

 terranean, Indian, and Chinese seas. 



The Aplysia dejnlans of Linnaeus, the type of this genus, early attracted the attention of 



naturalists •, its singular resemblance of forn\ to a crouch- 

 ing hare, was observed by the ancient Greeks and Romans, 

 who bestowed upon it the title it still bears. By them it 

 was regarded with no little superstition, and its haunts 

 along the coasts, supposed to be inhabited by the Nereids, 

 were shunned by the fishermen. 



THE BURSATELLID^. 



We may place here an animal of which little is known, 

 j^^^^^^^^ Leach's Bursatella, £. Zcachii, found in the Indian seas. 

 The descriptions given of it are very obscure ; it appears 

 to be destitute of shell, the body globular, the lower part 

 having an oval space, circumscribed by thick lips ; the 

 animal is furnished with curious swimming and branchial 

 appendages. Its place is not very definitely settled by 

 naturalists. Rang arranges it with the Aplysiada). 



LEACH S BURSATELLA. 



htemalis, 



THE BULLION. 



which are called Bubble-Shells, have a delicate globular shell, more or less inclosed in 

 the mantle. The foot is large and often furnished with lateral lobes, used 

 in swimming ; the gill is single, placed on the right side of the back and 

 concealed by the shell. They are carnivorous, and found generally on 

 the Atlantic shores. The Bulla anqjulla is beautifully mottled with white, 

 plum-color, and reddish. The B. velum is very elegant,' and of a light- 

 brown color ; the apex and base are both white, bordered with dark-brown 

 bands. The preceding species are found in the European and Indian seas. 

 The B. lic/naria, noted for having a testaceous gizzard, appears to be com- 

 mon on the British shores. There are several species on our coasts, but 

 all are small, mostly about one-third of an inch long. Among them is 

 the B. triticea ; the B. dcbilis, an exceedingly minute species ; the B. 



found in the stomach of codfish ; and the B. orijza, found south of Cape Cod. 



THE BULLA VELUM 



ORDER 3. HETEROPODA. 



The animals of this order, the NucleobrancMata of some authors, are all inhabitants of the 

 ocean, where they swim about rapidly, the whole structure of their bodies being adapted par- 

 ticularly to this mode of existence. The foot, when present, is converted into a broad, flattened, 

 fin-like organ, furnished with a small sucker, by which the animals adhere to floating sea-weed. 

 The whole body is usually compressed ; and it is by the fin-like action of the tail that the crea- 

 tures swim. The head is distinct, and usually famished with a pair of tentacles and eyes ; the 

 mouth is generally provided with a long proboscis. The animals are usually of a transparent 

 gelatinous texture ; they swim with the back downward, and appear to feed upon minute marine 

 animals. 



