801 



SIPHONOSTOMATA. 



SIREN-. 



802 



There are 180 recent species of Murex described. Their distribution 

 is world-wide. All the species of Murex yield a dye, and many of 

 them were used as well as Purpura Lapillus, for obtaining the Tyrian 

 purple of the ancients. Heaps of the broken shells of Murex truncwlus 

 are still to be found on the Tyrian shore. On the coast of the Morea 

 there is evidence of the employment of M. brandaris for the same 

 purpose. AI. erinacei. s, a very abundant species on some parts of our 

 coast, is called by fishermen Sting- Winkle. It makes holes in other 

 shell-fish with its beak. 



3Iurex ffgiits. 



The tjiphanotlomata and Entomostomata may be considered as the 

 two great tribes of carnivorous gastropods or trachelipod* appointed 

 to keep down the undue increase of the Conchifera and Herbivorous 

 Gastropods, whose shells the majority of those carnivorous testaceans 

 penetrate by means of an organ which makes a hole as truly round 

 as if it had been cut by an auger, and then feed on the juices of the 

 included animal. 



Dr. Buckland notices this habit with a view to the condition of the 

 testaceous inhabitants of the earlier seas of our planet with his wonted 

 felicity. " Most collectors," he says, " have seen upon the sea-shore 

 numbers of dead shells, in which small circular holes have been bored 

 by the predaceous tribes, for the purpose of feeding upon the bodies 

 of the animals contained within them : similar holes occur in many 

 fossil shells of the tertiary strata, wherein the shells of carnivorous 

 trachelipodg also abound ; but perforations of this kind are extremely 

 rare in the fossil shells of any older formation. In the green-sand 

 and oolite they have been noticed only in those few cases where they 

 are accompanied by the shells of equally rare carnivorous molluscs ; 

 and in the lias and strata below it, there are neither perforations, nor 

 any shells having the notched mouth peculiar to perforating carnivorous 

 species. It should seem from these facts that, in the economy of 

 submarine life, the great family of carnivorous trachelipods performed 

 the same necessary office during the tertiary period which is allotted 

 to them in the present ocean. We have further evidenc3 to show that 

 in times anterior to and during the deposition of the chalk, the same 

 important functions were consigned to other carnivorous molluscs, 

 namely, the testaceous cephalopoda : these are of comparatively rare 

 occurrence in the tertiary strata and in our modem seas ; but through- 

 out the secondary and transition formation?, where carnivorous tra- 

 chelipods are either wholly wanting or extremely scarce, we find 

 abundant remains of carnivorous cephalopods, consisting of the cham- 

 bered shells of Nautili and Ammonites, and many kindred extinct genera 

 of polythalamous shells of extraordinary beauty. The molluscous 

 inhabitants of all these chambered shells probably possessed the vora- 

 cious habits of the modern cuttle-fish ; and by feeding like them upon 

 young Tettacea and Crustacea, restricted the excessive increase of 

 animal life at the bottom of the moro ancient seas. Their sudden and 

 nearly total disappearance at the commencement of the tertiary era 

 would have caused a blank in the ' police of nature," allowing the 

 herbivorous tribes to increase to an excess that would ultimately have 

 been destructive of marine vegetation, as well as of themselves, had 

 they not been replaced by a different order of carnivorous creatures, 

 destined to perform in another manner the office which the inhabitants 

 of the ammonites and various extinct genera of chambered shells then 

 ceased to discharge. From that time onwards wo have evidence of 

 the abundance of carnivorous trachelipods, and we see good reason to 

 adopt the conclusion of Mr. Dillwyn. that in the formation above the 

 chalk the vast and sudden decrease of one predaceous tribe has been 

 provided for by the creation of many new genera and species possessed 

 of nimilar appetencies, and yet formed for obtaining their prey by 

 habits entirely different from those of the cephalopods. The desigu 



AT. H13T. DIV. VOL. IV. 



of the Creator seems at all times to have been to fill the waters of the 

 seas and cover the surface of the earth with the greatest possible 

 amount of organised beings enjoying life ; and the same expedient of 

 adapting the vegetable kingdom to become the basis of the life of 

 animals, and of multiplying largely the amount of animal existence by 

 the addition of Oanrivora to the Herbivora, appears to have prevailed 

 from the first commencement of organic life to tho present hour." 

 (' Bridgewater Treatise,') 



SIPUNCULOIDEA, an order of Echinodermatous Animals, em- 

 bracing the families Sipunmlidce, Priapulid(e, and Thalassemada. 

 This order is thus defined : The cutaneous envelope is coriaceous, and 

 free from calcareous corpuscles ; there is no calcareous ring about 

 the oesophagus ; the body is cylindrical ; the digestive canal usually 

 asymmetrical. 



1. The Sipunculida; (Syphon-Worms) have a retractile proboscis, at 

 the base of which is placed the vent, and round the extremity of which 

 there is a circle of tentacles. This family embraces the genera Syrinx, 

 Ripunculus, and Phascolosoma. 



Syrinx (Bohadsch) has a cylindrical proboscis shorter than the body, 

 having a circle of short-fingered tentacles around its tip. In his 

 ' History of British Star-Fishes,' Forbes refers three British species of 

 Sipunculns of other authors to this genus S. nudus, S. papillosus, and 

 S. Harveii. 



Sipnnculus (Linnteus) has a cylindrical proboscis about as long as 

 the body, and a circle of simple linear tentacles around its tip. The 

 following are British species of this genus : S, Bernhardus, S. John- 

 stoni, S. saccatus, S. tcnuicinctus, S. Forbcsii, S. granulosus, S. puncta- 

 tissimus, and S, Pallasii. 



2. The Priapulidce (Tailed-Worms) have a retractile proboscis with 

 no tentacles, and the vent at the end of a long thread-like tail. 



Priapulus (Lamarck) has the body truncated behind, and the tail 

 much branched and pointed. 



The only British species is P. caudattis, which is only rarely taken. 



3. The Thalassemada: (Spoon- Worms) have a body oval or oblong, 

 a proboscis with a long fleshy appendage; vent at posterior extremity, 

 tentacles none. 



Thalasscma (Cuvier) has a cylindrical borly rounded and smooth 

 behind ; the proboscis retractile, short, furnished at one side with a 

 long fleshy furrowed simple sheath, which is not retractile. T. Neptuni 

 is a British species. 



Echiurus (Cuvier) has a cylindrical body, set at its hinder extre- 

 mity with circles of bony points, and a proboscis as in Thalassema. 

 [EcHINODERMATA.] E. oxyuria is a British species. 



(Manual of Natural Jfiitory ; Gosse, Marine Zoology ; Forbes, 

 British Star-Fishes.) 



SIRE'DON, Waglor's name for the A-rototl. We subjoin an illus- 

 tration of the Axolotl from Messrs. DumcSril and Bibrou's great work 

 on Reptiles. [AXOLOTL ; AMPHIBIA.] 



Sired^n or Axolotl seen in profile ; a, mouth seen in front, open to show 

 the teeth. 



SIREN, a genus of Reptiles belonging to the Perennibranchiate 

 Batrachians. [AMPHIBIA.] It has the following characters : Form 

 elongated, nearly like that of the eels ; branchial tufts three on eacli 

 side ; no posterior feet, nor any vestige of a pelvis ; head depressed ; 

 gape of the mouth not wide; muzzle obtuse; eye very small ; the ear 

 concealed ; lower jaw armed with a horny sheath and several rows of 

 small teeth ; the upper jaw toothless ; but numerous small pointed 

 retroverted teeth occur on the palatal region. 



Dr. Garden appears to be the first who called attention to this form, 

 which is declared by Cuvier to be one of the most remarkable of the 

 class of Reptiles, aud indeed of the whole animal kingdom, from the 

 anomalies of its organisation, and its apparent relationship with 

 different families, and even classes. Dr. Garden (1765-1760) sent a 

 description of this reptile to Linnaeus and Ellis, and the former, 

 relying upon Dr. Garden's assurance that the Siren did not change its 

 form, established an additional order for it in his class Amphibia, with 

 the name of Meantes. 



Pallas, Hermann, Schneider, and Lacdpede however saw, as Cuvier 

 remarks, nothing more in the Siren than the larva of some large 

 unknown Salamander ; whilst Camper, followed by Gmelin, went so 

 far as to give it a place among tho fishes. The latter arranges it at 



3 F 



