633 



QDrcatfurg ot gtaturnl 



the surface of the shell has only been caused 

 by the contraction of the animal, and espe- 

 cially of the skin over the shell, from the 

 animal having been placed in very strong 

 spirits when caught. * * * The mantle is 

 free from the body on all sides at its oral 

 edge, and without any cartilaginous ridges ; 

 this edge is formed into a point on the centre 

 of the dorsal aspect, and into two mesial 

 processes, one situated on each side of the 

 anal funnel on the ventral side ; the funnel is 

 quite free from the mantle. The part of the 

 shell which is exposed is covered with minute 

 rugosities and indistinct reticulations, some- 

 what like the surface of a cuttle-fish bone. 



" The examination of this animal (oon- 

 tinues Mr. G.) confirms me in the opinion 

 which I expressed in the ' Synopsis of the 

 British Museum' (1840, p. 149.), that the 

 A mmonites, from their texture and the small 

 size of the last chamber, are internal shells, 

 and should be arranged with the Decapodous 

 Cephalopoda, being chiefly distinguished 

 from the Spirulce by the siphon being always 

 on the dorsal margin of the whorls, and the 

 septa being foliated on the edge. I am 

 aware that this opinion is not in conformity 

 with the ideas of many zoologists and com- 

 parative anatomists, for Mr. Owen, in the 

 last arrangement of these animals (Todd, 

 Ency. Comp. Anat.}, though he places the 

 Spirclce with the Dibranchiate Cephalopods, 

 places the Ammonites with Tetrabranchtata 

 next to Nautilus, with the following cha- 

 racter, " animal unknown, presumed to re- 

 semble the Nautilus." 



SPONDYLUS. A genus of Mollusca, for 

 the most part inhabiting a rough and foli- 

 ated bivalve shell, with spines and plaits ; 

 the valves closely united by two strong teeth. 

 Like the Pectens, the margins of the mantle 

 of the animal are garnished with two rows 

 of tentacula, and in the outer row there are 



several terminated with coloured tubercles : 

 in front of the abdomen is a broad radiated 

 disc with a short pedicle, capable of contrac- 

 tion and elongation ; and from its centre 

 there hangs a thread terminated with an 

 oval mass, the use of which is unknown. 

 They live at great depths in the sea, and 

 attach themselves to corals, &c. They are 

 also frequently found adhering to anchors, 

 cannons, and other iron articles that have 

 been for some time at the bottom of the sea. 

 Many of the species are very beautiful, and 



of very vivid colours, such as bright red, 

 pink, and yellow, or orange. Some of the 

 species of Spondylus, as the water-clam 

 (Si>oiidii1us varius\ form a series of chambers 

 by secreting successive layers of nacreous 

 shell at a distance from each other. The 

 genus is included in the Ostracean family of 

 the Acephalous Testacea, by Cuvier. The 

 Spondyli are eaten like Oysters ; and the 

 form of their shells is generally modified by 

 the surface of the objects on which they grow. 

 They are found in the Indian Ocean, the 

 Mediterranean, and on the American coasts. 



SPONGE. (Sjwnffia.) A cellular fibrous 

 tissue, or reticulated porous substance, found 

 adhering to rocks, and produced by minute 

 Polypi, . animals almost imperceptibly 

 sma'll, which live in the sea. This tissue 

 is covered in it? recent state with a kind of 

 thin coat of animal jelly, susceptible of a 

 slight contraction or trembling on being 

 touched its only symptom of vitality. 

 After death this soft gelatinous matter dis- 

 appears. Even' coast, from the Equator to 

 the highest Polar regions, furnishes some 

 species of Sponge ; but they exist in much 



[HE PORES 



greater abundance in warm latitudes than 

 in cold, and they attain also a much greater 

 size. "There are certain forms of organiza- 

 tion," observes Mr. Rymer Jones, " so closely 

 allied to both the animal and the vegetable 

 kingdom, that it is difficult to say precisely 

 in which they ought to be included. Such 

 are the Sponges, which, although by com- 

 mon consent admitted into the animal series, 

 will be found to be excluded, by almost 

 every point of their structure, from all the 

 definitions of an animal hitherto devised. 

 What .is an animal ? How are we to dis- 

 tinguish it as contrasted with a mineral or a 

 vegetable ? The concise axiom of Linnaeus 

 | upon this subject is well known, 'Stones 

 j grow ; vegetables grow and live ; animals 

 I grow, live, and feel.' The capability of 

 ! feeling, therefore, formed, in the opinion of 

 i Linnaeus, the great characteristic separating 

 j the animal from the vegetable kingdom ; 

 yet, in the class before us, no indication of 

 sensation has been witnessed ; contact, how- 

 i ever rude, excites no movement or contrae- 

 i tion which might indicate its being perceived} 



