GYRIXUS. 



[ 368 J 



GYROSIGMA. 



surface of pools or rivers, whence it has 

 received the popular name of whirligig. 



The body is ovate or elliptic, and de- 

 pressed, the elj-tra black and shining. The 

 antennae are short and retractile within a 

 cavity in front of the eyes; the basal joint 

 minute ; the second large, globular, and fur- 

 nished externally with an ear-like joint 

 fringed with coloui'less, flattened, hair-hke 

 processes ; the remaining seven j oints form 

 a clavate mass, being very short and closely 

 united, the first commencing by a very 

 narrow base or pedicle. The eyes are di- 

 vided by a transverse septum into two parts, 

 the upper of which serves for viewing ob- 

 jects in the air, the latter those in water ; 

 by some authors these insects are described 

 as possessing fom- distinct eyes. The tei'- 

 minal segment of the abdomen is fm-nished 

 with two retractile ciliated lobes. The two 

 fore legs are long, and of the ordinary form, 

 whilst the four hind legs (PI. 34. fig. 5), 

 wliich are used as oars, are short, flat, and 

 dilated; the femur (d) and tibia {c) some- 

 what triangular, the tibia also fringed with 

 short spines and long flattened filaments ; 

 in the middle pair of legs the latter exist 

 on both margins, whilst in the hind legs 

 these are present only on the outer mar- 

 gin. The tarsi (a) are five-jointed, the 

 three basal joints produced on the inside 

 into long, flat, leaf-like lobes fringed with 

 spines ; the fourth joint is of about the same 

 size, and semicircular, the fifth being very 

 short and attached to the fourth near the 

 end, and both are fringed on their outer 

 margin with flattened filaments resembling 

 those upon the tibia ; all the tarsi are fur- 

 nished with two distinct claws. 



The anteriol- tarsi of the male differ from 

 those of the female, as in Di/tiscus. Tlie 

 circulating currents can be seen in the hind 

 legs. 



The larva (PI. 35. fig.19), which is aquatic, 

 is of a dirty-white colour, long, narrow, aud 

 depressed, resembling a small centipede ; it 

 consists of thirteen segments including the 

 head. Its antennae are filiform aud four- 

 jointed ; the eyes numerous and tub;-rcular, 

 grouped on each side of the head. The 

 three pairs of legs are attached to the eight 

 anterior segments of the body ; the remain- 

 ing segments are furnished on each side 

 with a branchial filament, excepting the 

 last, which has two of them, and four mi- 

 nute conical points, bent downwards, and 

 used by the insect when in motion. 



BiBL. Westwood, Introd. i. 105; Ste- 

 phens, Br. G'oleop. 7e>. 



GYROC'ORiy, St.— A genus of Peri- 

 trichous Infusoria. 



Char. Free, with one or more spiral or 

 circular wreaths of cilia, stylate poste- 

 riorly. 



G. o.vyicra. With anterior eye-spot ; mo- 

 tion revolving, rapid. Stagnant water. 

 (Kent, Lif. U40.) 



G YRODAC T YLUS, Nordm.— A genus 

 of Trematode Eutozoa. 



G. aurivulutns (PL 21. fig. 7) is often 

 foimd adhering to the gills of fishes, as the 

 carp, stickleback, &c. 



BiBL. Dujardin, Helminth. 480; Wa- 

 gener, Qn. M. Jn. l60l, 19G; Cobbold, 

 Faras. 465. 



GYROPH'ORA, Ach.— A genus of 

 Phylloidei (Lichenaceous Lichens), com- 

 bined with UmbiUcaria by many authors. 



GYliOPOREL'LA, Gumbel.-A small 

 cylindrical Foraminifer, belonging to the 

 iJactijloporiyia, and consisting of ring-like 

 segments traversed by simple canals. Its 

 several species constitute large masses of 

 Triassic limestone in the Alps. 



BiBL. Giimbel, Abh. Miinchen, xi. 268. 



GYR'OPUS, Nitzsch. — A genus of man- 

 dibulate Auoplura (Insects), of the family 

 Liotheidae. 



Char. Tarsi two-jointed, -n-ith a single 

 claw. 



Mandibles without teeth ; maxillary palpi 

 conical and four-jointed; labial palpi none; 

 antennae four-jointed; thorax two-jointed; 

 abdomen eight-jointed. 



G. ovalis (PI. 35. fig. 8). Head ferrugi- 

 nous, transverse, with a lateral produced 

 lobe on each side ; thorax and legs ferrugi- 

 nous; abdomen nearly orbicular, yellow- 

 ish white ; claws long, curved, and strong ; 

 length 1-48"; found on the guineapig 

 (Cavia cvbaj/a). 



G. yraciUs. Head and thorax ferruginous; 

 abdomen elongate, segments with a trans- 

 verse striated iDand at each suture ; claws 

 very short and minute; length 1-36"; also 

 on the guineapig. 



3 other species : on the agouti, the sloth, 

 and the peccary. 



BiBL. Denny,Anqplur.Monu</r. ; Megnin, 

 Paras. 94. 



GYROSIG'MA, Hass. See Pleuro- 



SIGMA. 



