TEETH OF GASTEROrODA, 541 



strong, well developed teeth ; they are all animal feeders. 

 Loven describes those of the cuttle-iish (Sepia officinalis, 

 Plate V. No. Ill), as like Pteropoda, formula of teeth, 

 3 • 1 • 3. The Sepia is also furnished with a retractile 

 proboscis, and a prehensile spiny collar, apparently for the 

 purpose of holding its prey while the teeth are employed 

 in drilling or abrading it. In the Squid (Loligo, No. 113), 

 the medians, broad at the base, approach the tricuspid form 

 with a prolonged acute central cusp ; while the uncini are 

 much prolonged and slightly curved. The lingual band 

 increases in breadth towards the hinder part, in some in- 

 stances to twice the diameter of the anterior. The band, 

 when mounted dry, forms a fine object for the black- 

 ground illuminator, or side reflector. The lingual band of 

 Octopus tuhercidatus differs slightly with Sepia. 



The Nudihranchiata have become more attractive since 

 the publication of the valuable and beautifully-illustrated 

 monograph of Messrs. Alder and Hancock. The nudi- 

 branchs are without a shelly covering, slug-like in their 

 appearance, and most voracious feeders, greedily devouring 

 zoophytes, sponges, &c. (Plate IX. 6.) They possess the 

 remarkable property of restoring lost parts ; their powers 

 of endurance are great, so that they may be kept alive for 

 some time in a small glass jar of sea-water. AVhile keep- 

 ing a specimen of the Piplida in confinement, the Eev. 

 Mr. Lowe noticed on several occasions a display of a bril- 

 liant phosphorescence. Many of the genus Dorididce and 

 Eolidida are infested with parasitic Entromostraca, which 

 either live freely on the surface, under the skin, or adhere 

 to the branchiae of ohe animals. Oncidoris hilamellata (the 

 Sea-lemon) belongs to the Dorididse ; its mouth is provided 

 with a narrow band of strong hooked teeth (Plate Y. No. 

 120), which in some species are serrated ; all are provided 

 with mandibles, consisting of two horny plates uniting 

 near the fore part. The median row of teeth are small and 

 inconspicuous ; the band is represented by the formula 

 2 • 1 • 2. A. portion of the mandible of Apli/sia hyhrida 

 (the Sea-hare) is shown in Plate V. No. 112. 



Patella radiata (the Eock-limpet). — The band of this 

 mollusc. No. 116, may be readily distinguished from the 

 3ommon limpet of our coasts ; the remarkably long ribbon- 



