T E R 



221 



T E R 



globular PHOLAS fixed at the end of a tube, and has in 

 fact the exterior characters of the Pholades. It carries an 

 escutcheon on the umbones, and within it is provided with 

 those appendages which so readily distinguish the Tere- 

 dines and the Pholades from other genera. The shell is 

 always external, and soldered by the posterior extremity of 

 its valves to the anterior part of the tube, which is very 

 thick and terminated by a blackish part of a horny appear- 

 ance, whose internal surface is sometimes divided into 

 eight regular carinations. 



M. Deshayes, in his Tables, gives two species, Teredina 

 personata and a new species, both from the tertiary beds 

 (Eocene of Lyell). In the last edition of Lamarck no 

 notice is taken of the new species, and to the second 

 species, Teredina bacillum, recorded by Lamarck, is ap- 

 pended a note stating that this last does not belong to the 

 genus Teredina; and that, according to the description 

 and figure of Brocchi, it can only be a Clavagella or a 

 Fistulana ; but that it is not Clavagella tibialis, as M. de 

 Blainville believed. 



Tcrcilina pcrsouata. (Courtagnon, fee.) 



n. tube with valves; 6. the other termination of the t<ibe; r, awcsmry valve ; 

 d, Talves with accessary valve in its place. (G. B. Sowerby.) 



TERE'DO, the name given by Linnaeus to a genus of 

 testaceous mollusks, highly interesting on account of the 

 i svages which one of the species commits upon submerged 

 wood. 



Linns- us, in the twelfth edition of the ' Systema Naturae,' 

 placed the genus among his Verntes testacea, between 

 S/'r/iii/n ami Sttbella : nor is this certainly inapt posilion 

 to be wondered at when we consider the very infant state 

 of malacology in his day. 



Cuvier, in his last edition of the ' R4gne Animal,' makes 

 Teredo one of the genera of his Enfermfa, the fifth family 

 of \mAcephalous Testaceans, arranging the genus between 

 I'luiliw and Fixtulana. 



M. de Blainville arranges the genus in the tenth family 

 (Adesmacea) of his Pyloridians, between Teredina and 

 Fistulana, immediately after which comes Septaria. 



Lamarck had placed the genus among his Tubicolees, 

 and M. Rang adopts that arrangement, giving it a position 

 however between Jouannetiannil Fistulana, next to which, 

 and immediately before TEREDINA, Septaria appears. 



Lamarck ended with this genus his Tubicoteen, which 

 are immediately followed by the Pholadaires. Teredo is 

 immediately preceded by Teredina, and this again by 

 typtaria. In speaking of the last-named genus, M. 

 Deshayes, in the last edition of Lamarck, observes 

 that although the animal and the shell of Septaria 

 are not known to him, the great portions of its testa- 

 ceous tube or sheath, which he had seen, convinced 

 him that the animal is analogous to that of the Fixtiilunr/-. 

 which differ from it principally in size only ; and because 

 its two anterior siphons are very long, and form for them- 

 *elves each a particular testaceous sheath. The animal 



ought therefore to have posteriority, he remarks, a bivalve 

 shell, which had escaped those who have collected the 

 great tube, or the portions of it which we see in cabinets. 

 M. Deshayes goes on to state that he has only seen a few 

 septa, unequally distant and entirely incomplete. Some 

 Fistulana;, he adds, have also vaulted septa in the pos- 

 terior part of their sheath ; but the diminished or anterior 

 part of this offers only particular tubes projecting out 

 wards (1835). 



Again, when Lamarck concludes his observations by 

 saying that, for the rest, the Septaria is hardly anything 

 but an exaggerated Fistulana, and scarcely deserves to 

 be distinguished as a genus, M. Deshayes declares that if 

 we substitute for the word Fistulana that of Teredo, these 

 remarks would be perfectly just. This genus, he adds 

 (Lamarck's Septaria), which had been believed to be pe- 

 culiar to the seas of India, has been found some years since 

 in the Mediterranean ; and he refers to the paper pub- 

 lished on that animal in the ' Annales des Sciences et de 

 1'Industrie du Midi de la France,' Marseille, 1832, by M. 

 Math6ron, in which that naturalist proves the animal of 

 Septaria to he similar to that of Teredo ; and this resem- 

 blance, says M. Deshayes, in conclusion, confirms his own 

 opinion of the necessity of uniting the Septarice and the 

 Teredines. 



Mr. Swainson (Malacology, 1840) places Teredo with the 

 subgenera Teredo and Teredina, at the end of the ' Pho- 



Mr. J. E. Gray arranges Teredo between Teredina and 

 Bankia, under his Pholada, the first family of his second 

 order (Cladopoda) of Conchifera. Septaria is introduced, 

 with a query, into his second family, Gastrochcsntdce. 

 ORGANIZATION. 



It is now 36 years since Sir Everard (then Mr.) Home 

 laid before the Royal Society, with the assistance of Mr. 

 Clift in making the drawings, and the aid of Sir Benjamin 

 (then Mr.) Brodie, his Observations on the Shell of the 

 Sea-Worm found on the Coast of Sumatra, proving it to 

 belong to a Species of Teredo, with an account of 

 the Anatomy of the Teredo Navalis. Sir Everard remarks 

 that the internal structure and economy of Teredines were 

 so little known, and so much of what was said of them bv 

 Sellius was so vague, that it became necessary to acquire 

 an accurate knowledge of the common Teredo navalis, 

 before any adequate idea could be formed of the new 

 species, which he names Teredo gigantea. 



On examining the shell of Teredo navalis while in the 

 wood, Sir Everard found its external orifice very small, 

 just, large enough, in fact, to give a passage to the two 

 small tubes. The greatest thickness observed was ^ of an 

 inch. The canal in the wood at its termination, and for 

 an inch in length, was not lined with shell, but smeared 

 over with a dirty green-coloured mucus, which was also 

 spread upon the last-formed portion of shell. According 

 to Mr. Hatchett's analysis, the shell of Teredo navalis was 

 perfectly similar to that of Teredo gigantea, being devoid 

 of phosphate of lime, and composed of 97 parts of carbo- 

 nate of lime and 3 of animal matter. 



While the animal was in the shell alive and undisturbed, 

 what is termed the head was in contact with the end of the 

 canal in the wood ; but, on laying the head bare, it was 

 drawn in for an inch into the shell. The body of the animal 

 filled the area of the shell completely, but appeared much 

 smaller when taken out, in consequence of the sea-water 

 which it contained having escaped. The largest of the 

 worms examined which were of different lengths measured 8 

 inches in length. Many of them were alive 24 hours after 

 being removed from their shell, and in these the heart was 

 seen to palpitate. The blood in the vessels going to the 

 head was red, as also the parts near the liver ; but this 

 colour disappeared soon after death. 



The head of the worm was enclosed between the two 

 concave boring shells, so that what Sir Everard calls the 

 face was the only part exposed. These shells were united 

 together on what is termed the back part of the head by a 

 very strong digastric muscle, having a middle tendon from 

 which the fibres go off in a somewhat radiated direction. 

 partly for insertion into the concave surface of each shell, 

 and partly into a long semicircular process projecting from 

 the posterior part of each shell. The two inclose the oeso- 

 phagus and otlier parts surrounding it. The double muscle 

 was inclosed in a smooth shining fascia, When first ex> 

 posed it was of a bright red. 



