935 



SWIMMING-BIRDS. 



SYLVIAD^E. 



line which lies evenly between d ef and a line drawn par.illel to it 

 through h. The fiah being in motion whilst the tail moves from side 

 to side, according to Borrelli, itde-cribes an ellipse instead of a circular 

 arc, which would be the case if the body were stationary and the tail 

 only moving. The velocity with which fishes move, and the continu- 

 ance of their movements, are enough to give us an idea of the great 

 strength of their muscles, especially when we reflect on the density of 

 the fluid which is opposed to their speed. Those fishes which have 

 occasion for great speed (such as the shark, as well as other predaceous 

 fishes), have their tails forked (fy. 16). In these the area of the surface 



Fig. 16. 



Tail of Shark. 



of the tail is in the inverse ratio of the distance from its aria of motion. 

 This figure is that which may be considered best adapted for great 

 velocity of progression. When the surface of the tail increases as its 

 distance from the centre of gravity of the animal, the muscles act at a 

 mechanical disadvantage, and the animal can proceed but slowly. In 

 whales the surface of the tail is proportional to the enormous bulk of 

 the body ; but the plane of the tail is transverse, or in the mesial 

 plane of the body, instead of being perpendicular as in fishes ; and its 

 action is at right angles to that of fishes also. The force of the tail 

 must be very great, inasmuch as they have been observed to throw 

 themselves quite out of the water, many feet in height, into the air. 



As we descend lower in the scale of organised beings, we find an 

 illimitable number of aquatic animals. The lobster, prawn, and 

 shrimp, swim backwards by the action of the tail ; tut in these the 

 effective stroke is during the flexion of the tail, and not the extension, 

 as in fishes. Many insects are also aquatic, such as the Dytiscus and 

 others. [FLTIMO ; LOCOMOTION IN ANIMALS.*] 



SWIMMING-BIRDS. [NATATORES.] 



SWINE. [SDUXE.] 



SWORD-FISH. [ScOMBMDJs; XIPHIAS.] 



SYCAMORE. [AcER.1 



SYCAMORE-FIG. [Ficpg.] 



SYCO'CRINUS. [ECHINODERMATA.] 



SYLLIS. [ANNELIDA.] 



SYLVIA. [EBTTHACA; SYLVIADJS.] 



SY'LVIAD^E (Vigors), a family of Birds belonging to the tribe 

 Dentirostrct and the order Intaiorct. 



Mr. Vigors remarks that the Sylviadcf, the Warblers of our British 

 ornithologists, assimilated as they are to the Merulidce in the sweetness 

 and compass of their vocal power, are separated from that family chiefly 

 by their more delicate structure and more subulate bill. That portion 

 of the Linnsean Motacilla, or rather of the Sylvia of Latham, he ob- 

 serves, which Bechstein has separated from the genus under the title 

 of Accentor, in conjunction with that which embraces the Nightingale 

 (Sylvia lutcinia), appears to be the group most nearly approaching the 

 Thrushes by the comparative strength of its formation. Here also, 

 perhaps, he thinks we may find the Uylophilus (Temm.) of the New 

 World, and the lora (Horf.) of the East, to be united by their stronger 

 bills. Hence, he continues, a number of intervening groups (among 

 which Brachypteryx, and that which includes Sylvia rubecola, the Red- 

 breast, are specially noticed by him) conduct the inquirer by their 

 gradually lessening bill and more slender form to those birds in which 

 the delicate body, the tapering legs, and the gracile and subulate bill 

 point out their typical supremacy in the family. To these latter groups 

 he considers Afelizophilut (Leach), the Dartford Warbler, and Malurus 

 (Vieill.), the representative of Sylvia in Australasia (in both of which 

 the bill deviates from that of the conterminous genera in the culmen 

 being somewhat arched), nearly allied, and also the Wrens (Troglo- 

 dyla and Reyulua, Cuv.). To these he makes succeed a number of 

 groups whose lengthened tarsi indicate that their natural station is on 

 the ground, such as Budyta (Cuv.), the true Motacilla of authors ; 

 and Enicurui (Temm.) ; and here he would add Meyalurut (Horsf.) ami 

 Anthui (Bechst.), which unite, in his opinion, the Lentirottrei with the 

 Conirottra, by means of the Larks (Alauda of authors). Mr. Vigors 

 then statta that Kaxicola (Bechst.) is nearly allied to the Larks in its 

 terrestrial habits and general conformation ; but which, by its increas- 

 ing bill, brings us round to the earlier groups of the present family, 

 and thence to the Merulidce, with the section of which it is, he thinks, 

 nearly connected. The circular disposition by which the extremes of 

 different families may be brought into contact with each other, explains, 

 in hi view of the case, the manner in which the genus Saxicola, the 



* This article forms the concluding part of LOCOMOTION ix ANIMALS, for 

 which we are indebted to Mr. J. Bishop. 



; 1 



[ ] Saxicolma. 



section of Merles Saxicoles, the genus Myiotkera, and the more deli- 

 cate forms of Thamnophilus, all birds decidedly approaching each other, 

 yet belonging to the different families of Sylviadce, Merulidce, and 

 Laniadce, still preserve their union, and are brought together into a 

 conterminous assemblage. 



The True Wrens display, in his opinion, so close a similarity iu 

 their general appearance and habits to Pants (Linn.), the Titmouse, 

 that we may at once acknowledge the affinity between the latter 

 family and the Pipridce, upon which family he enters by the Titmice. 

 (' Linn. Trans.,' voL xiv.) 



Mr. Swainson thus arranges this family, " marked by peculiarities of 

 habit no less than by a variation of structure applied to such habits :" 



Circles. Sylviadce, or Warblers. Sub-Families. 



1. Typical . . | Bi "j al ry Slender> com l> re88ed ; Iatera l to" \Sylmana. 



2. Subtypical . Bill and general structure more robust . . PhilomeHna. 



Bill depressed at its base ; legs lengthened ; 

 strong 



3. Aberrant . { Claws lengthened, and but slightly curved ; \ 



live upon the ground J 



Bill strong, almost entire : hinder toe and ) _ 

 claw large \ ?<"">" 



Of this group the Motacillina;, in Mr. Swainson's opinion, form the 

 most aberrant division. Purely insectivorous, they are, he remarks, 

 well exemplified by the four common and well-known species distri- 

 buted through this country and Europe generally. " They live," says 

 Mr. Swainson, " almost entirely upon the ground, where alone they 

 seek their food, which consists entirely of insects : damp meadows, 

 and the sides of standing or running waters, are the favourite haunts 

 of these birds ; and they run with such celerity, that, in this respect, 

 as well as in their general black and white plumage, they can only 

 be compared to the plovers." He considers them, in fact, as col- 

 lectively representing the touuirostral type of the perchers ; or, what 

 is the same, the grallatorial type among birds. 



Mr. Swainson enters among the Parlance, or Tits, by the American 

 genus Seiurus; and among the True Warblers (Sylviance) by the 

 genus Culicivora, comprising the Gnat-Snappers. 



The union of all these sub-families is, in Mr. Swaiuson's view of 

 the case, effected by the Gryllivora, a genus of SaxicoUnce uniting to 

 Enicurus, which stands at the confines of the Wagtails (Motacillince). 



The following genera are comprised under this family, according to 

 Mr. Swainson's arrangement : 



Sylviadce. Size universally small. Bill very slender, distinctly 

 notched. Feet formed for walking, perching, or climbing. Tarsus 

 slender, lengthened. (Sw.) 



Saxicolinte, Stonechats. Bill depressed at the base : gape with 

 diverging bristles. Feet lengthened. Tail rather short. Head large. 



Genera: Gryllivora, Sw. ; Thamnobia, Sw. ; Saxicola, Bechst.; 

 Erythaca, Bechst. (Robins) (with the sub-genera Erytkaca, Sw., and 

 Sialia, Sw.) ; Petroica, Sw. 



Philomelince, Nightingales. General structure larger and more 

 robust than the typical warblers. Feet formed for perching. 



Genera: Phcenicura, Sw. (Redstarts); Philomela, Antiq. (Night- 

 ingales) ; Curruca, Bechst. ; Bradypetus, Sw. ; Ayrobates, Sw. 



Sylviance, True Warblers. Size very small. Structure weak. Bill 

 very slender, straight, and with the under mandible much thinner 

 than the upper. (Sw.) 



Genera : Orthotomus, Horsf. ; Malurus, Vieill. (with the sub- 

 genera Hemipteryx, Sw. ; Drymoica, Sw. ; Melizophilua, Leach ; Malu- 

 rus, Vieill.); Sylvia, Lath (with the sub-genera Sylvia, Acanthiza, 

 Horsf. and Vigors; Reyulus, Ray; and Cyanotis, Sw.); Culicivora, 

 Sw. ; Praticola, Sw. 



Parlance, Titmice. Bill either entire or very slightly notched, 

 more or less conic. Tarsus never shorter than the hind toe, which is 

 large and strong. Lateral toes unequal. (Sw.) 



Genera : Setophaya, Sw. ; Sylvicola, Sw. (with the sub-genera 

 Dumecola, Sw. ; Sylvicola, Sw. ; Vermivora, Sw. ; Mniotilta, Vieill. ; 

 Zotterops, Horsf. and Vigors); Parus, Linn, (with the sub-genera 

 jEgithina, Vieill. ; JByithalus, Vig. ; Parus, Linn. ; Parisoma, Sw. ; 

 and Hylophilus, Ternm.); .Accentor, Bechst. (with the sub-genus Seiurus, 

 Sw.); Trichas, Sw. 



Motacillince, Wagtails. Bill lengthened ; very straight and slender. 

 Legs long, formed for walking. The hind toe much longer than the 

 rest. Wings pointed. Tail narrow, and much lengthened. (Sw.) 



Genera: Lessonia, Sw. ; udytes,Cuv.; Motacilla, Linn. ; Enicurus, 

 Temm. ; AnAius, Bechst. 



The family stands between the Merulidce and the Ampelidce. 

 (' Classification of Birds.') 



The Calamoherpince, Sylvince, SaxicoUnce, Motacillince, Parince, and 

 Sylvicolince, are arranged by Prince Bonaparte under his family of 

 Turclidcn. [MEKULID.E.] 



Mr. G. R. Gray makes the Sylviadce the first family of his third 

 tribe (Dcntirostret) of Insessores, with the following sub-families : 



1. Malurince. 



Genera : Orthotomus, Horsf. (Edela, Less.) ; Prinia, Horsf. ; 

 Drymoica, Sw. (Sylvia, Lath.) ; Cyanotis, Sw. (Sylvia, Vieill., Tachuris 



