12 



SYSTEMATIC HISTORY OF THE I^EUSOKIA. 



ratus, and a simple foot with a suction-disc and sometimes a bunch of cilia 

 at its extremity. P. elliptica has a hairy process projecting between the two 

 lobes of the rotary organ, and P. Patina has a rounded prominence in a similar 

 position on the dorsal surface. Muscles, often transversely striated, occur in 

 all the species, as also a constricted alimentary canal with glandular appen- 

 dages and an ovarium. Some have a contractile vesicle and a water-vascular 

 system. 



Pterodina Patina (Brachionus Pa- 

 tina, M.). — Figure roimd, or oval com- 

 pressed. Lorica membranous, crystal- 

 line, somewhat scabrous near its broad 

 margin, and slightly excavated anteriorly 

 between the two lobes of the rotary 

 organ. The latter not double, as de- 

 scribed by Ehrenberg, but with an an- 

 terior and posterior depression, from the 

 latter of which extends a single rounded 

 process. Cilia in two rows, prolonged 

 to the oesophageal bulb. Stomach ciliated 

 internally, widely expanded posteriorly. 

 Short intestine also ciliated, and termi- 

 nating at the base of the foot. Two 

 pyriform glands in front of the stomach. 

 Two red specks opposite the margin of 

 the rotary organ ; their red pigment has 

 a sharp spherical figure ; according to 

 Leydig, an obvious refracting body pro- 

 jects from the anterior convex edge of 

 each. Two large longitudinal muscles. 

 On each side of the stomach a water- 

 vascular canal, but without either tags 

 or contractile sac. Ovary horseshoe- 

 shaped. Free extremity of the foot with 

 a bundle of setae. 



This animal was noticed by Perty to 

 have the peculiarity of assuming an ap- 

 parently lifeless state for half an hour or 



an hoiu* at a time, lying in one spot, 

 often on the smface of the water, with 

 no other sign of life than that afforded by 

 movements of the oesophageal cilia, and 

 occasionally of the jaws. 



This species is very delicate and tran- 

 sparent. XXXV. 502 represents a side 

 view, and 503, 504 under views, — the 

 latter having the wheels extended, the 

 former having_ them withdrawn, and the 

 anterior margin bent in, so that the eyes 

 appear near the middle of the lorica. 

 The internal organization is further 

 shown in xxxvni. 29. Foimd in sum- 

 mer among Lemnce and Ceratophylla. 

 Leng-th about 1-120". 



P. elliptica. — Lorica membranous, el- 

 liptical, with a narrow, smooth margin, 

 front entire (not excised). The two 

 wheels united by a brow fmnished with 

 setae. Eyes distant. Amongst Con- 

 fervae. 1-120" to 1-108". 



P. clypeata {Brachionus clypeatus, M.). 

 — Lorica membranous, oblong, naiTOw, 

 smooth at the margin ; there is a frontal 

 portion, or brow, connecting the two 

 wheels, but no setae. The eyes approxi- 

 mate, (xxxv. 505 a dorsal view, with 

 the wheels extended.) In sea-water. 

 Length 1-120" ^ the shell 1-144". 



The next genus, Pompholyx, instituted by Mr. Gosse, is considered by him 

 to be a member of this family. 



Genus POMPHOLYX (Gosse, A. N. H. 1851, vol. viii.). — Two frontal 

 eyes ; foot wanting ; rotary organ double in the rear, entire in front ; eggs 

 attached behind after deposition. The name alludes to the resemblance of 

 the lorica to a round flat smelling-bottle. 



PoMPHOLYX complanata. — Lorica 

 much depressed, nearly circular, with 

 the lateral edges rounded ; anteriorly 

 truncate j occipital edge gradually rising 



to a central blunt point j mental ridge 

 with two rounded lobes, divided by a 

 central notch, Lorica 1-300". 



Of the ensuing genera, established by Ehrenberg, we have only met with 

 the description of species ; of one, indeed, with only a sketch of its relations. 



Genus LARELLA (Ehr.). — The following species of this new genus, the 

 characters of which we have not met with, is named by Ehrenberg. 



Larella Piscis. — Body with equal eyes. Length 1-190" to 1-280". Berlin, 

 setae, and three long fine hairs placed on Wemeck has also seen this species, 

 each side the mouth, with two frontal 



