OVUM. 



[ 571 ] 



PACHYGNATHUS. 



1880; His, Mensckl.Emhri/0,1880; Reichert, 

 Menschl. Frucht. 1873 ; Girdwoyn, Mai. d. 

 (Eufs (tish), 1880. 



OVUINI OF Plants. See Ovule. 



OXALATES. See the bases. 



OXYR'RHIS, Duj.— A genus of Flagel- 

 late Infusoria, belonging to the family 

 Thecamonadina. 



Char. Body ovoid - oblong, rugose, ob- 

 liquely notched in front and prolonged into 

 a point ; several flagelliform filaments (two, 

 Kent) arising laterally from the bottom of 

 the notch. 



O. marina (PI. 31. fig. 54). Body colour- 

 less, subcylindrical, rounded behind ; ma- 

 line ; length 1-500". 



BiBL. Dujard.7«/.347; Pritchard, Inf. 513. 



OXYT'IMCHA, Bory, Ehr.— A genus of 

 Hypotrichous Infusoria", of the family Oxy- 

 trichina. 



Char. Closely resembling Stylonychia \ 

 but the front of the bodv not produced. 



O. penioneUa, E. (PI. 31. fig. 52). Body 



whitish, smooth, slightly depressed, equally 

 rounded at the ends, often somewhat broader 

 in the middle ; head not distinct ; mouth 

 ciliated; tail with bristles. Freshwater; 

 length 1-720 to 1-280". 



0. ffibba E. (PI. 31. fig. 53). Body white, 

 lanceolate, obtuse at each end, ventricose 

 in the middle ; ventral surface flat, with a 

 double row of setge ; mouth large, rounded. 

 Freshwater; length 1-240". Other species. 



According to Haime, Oxytricha is the 

 larva of Aspidisca. 



BiBL. Ehr. hif. 363; Duj. Inf. 416; 

 Haime, Ann. Sc. Nat. 3. xix. 109 ; Clap, et 

 Lachm. Maudes, 139 ; Kent, Inf. 786. 



OXYTRICHI'NA.— A family of Hypo- 

 trichous Infusoria. 



Char. Carapace absent; body depressed, 

 with vibratile cilia, setae, or cii-ri, and non- 

 vibratile styles or hooks. Movement crawl- 

 ing. Alimentary orifices two, neither ter- 

 minal. 



Genera : — 



( 



Marginal cirri . 



{The anterior part of the body not pro- 

 longed as a neck, furnished with cirri OTytricha. 

 The anterior part of the body neck- like, 

 and covered with cirri S/ichochieta. 



(.Foot-cirri not arranged in rows Stylonychia. 



{TTx-iu e ,, r Foot-hooks / No dorsal bristles Euplotes. 



Withtrontal I ^^^^ 1 Dorsal bristles Schizopus. 



ciT" LNo foot-hooks Cumpylopus. 



Without frontal cirri Aspidisca. 



-I 



BiBL. Ehr. Inf. 362 ; Pritch. Inf. 639 ; 

 Clap, et Lachm, Etudes, 168. 



OXYUR'IS, Rud. See Ascaris. 



OY'STER {Ostrea).—k. genus of Lamel- 

 libranchiate Mollusca. 



The giUs of O. edulis, the common oyster, 

 show the ciliary movement ; but it is not so 

 easily seen in this as in the marine mussel. 



The sheUs of the fry or 'embryo oysters' 

 exhibit the black cross and an imperfect 

 set of coloui'ed rings with polarized light. 



PACHNOC'YBE, Berk.— A genus of 

 Isariacei (Hyphomycetous Fungi), some- 

 what confused by authors with Doratomyces, 

 Corda, and Periconia, Xees. These plants 

 have an erect filiform stem, composed of 

 conjoined filaments, capitulate above, the 

 head being pruinose (not floccident), with 

 crowded simple spores. The pedicels are 

 mostly brownish or blackish, the spores 

 light-coloured ; the entire plants from 1-24 

 to 1-6" high. Several species occur on 

 rotten wood, stems, &c, 



BiBL. Berk. Hook. Br. Fl. ii. pt. 2. 333 ; 



Ann. N. H. 2. v. 465 ; Fries, Sum. Veg. 

 467, 



PACHYG'NATHUS, Duges.— A genus 

 of Trombidina (Acarina) . 



Char. Palpi conical, last joint scarcely 

 forming a claw; mandibles stout, chelate; 

 body entire, naiTowed in front ; coxfe dis- 

 tant ; legs gxessorial, sixth joint very long, 

 seventli very short; anterior legs longest 

 and stoutest, 



P. vehitinus (PI, 6. fig. 34), the only spe- 

 cies. Foimd in autumn, imder damp stones. 

 Hairs covering the body short, fiat, and 

 curved, giving it a velvety aspect. Body 

 infiated, narrowed in front, the narrowed 

 portion with two projecting brownish eyes. 

 Insertions of the legs in two groups, not 

 far distant, or from the median line ; second 

 pair of legs shortest ; in all the sixth joint 

 very long, the seventh very short and nar- 

 row (6), as in Tetranychus, Megamerus, and 

 Paphignathus ; claws two, large ; rostrum 

 projecting; palpi (a) short, about twice the 

 length of the labium ; mandibles very large 

 and stout at the base. Movement slow, 



BiBL. Duges, Ann. Sc. Nat. 2, ii. 54; 

 Gervais, Walck, Apter. iii. 171. 



