HYDROSTATICA. 429 



globules, and finally, partly filiform and susceptible of considerable 

 elongation, form a cluster or garland at the inferior extremity*. 



Hippopus, Quoij and Gaijm., 

 Where there are merely lateral vesicles, almost semi-circular, or 

 shaped like the foot of a horse, and crowded into two ranges, thus 

 forming a sort of spike comparable to that of certain grasses, from 

 Avhich also depends a kind of garland that crosses all the preceding 

 I^arts. The united contraction of these vesicles enable the animal to 

 move rapidly f. In 



CUPULITA, 



The vesicles are regularly attached to the tAvo sides of a frequently 

 very long axis ;[:. 



Racemida, Ciw., 

 Where all the vesicles are globular and small; each one is furnished 

 with a little membraine, and they are united in an oval mass Avhich 

 moves by their joint contractions §. 



Rhizophyza, Per., 



Where there are no lateral vesicles, but merely a superior bladder and 

 an elongated stem, along which the tentacula are suspended, some 

 conical and the others filiform ||. The 



Stephanomia, Per., 

 Appears to be a. third comljination, where the lateral bladders, which, 

 in Physsophora proper, adhere to the top of the stem above the ten- 

 tacula, extend along its length and intermingle with tentacula of 

 various forms ^. 



It is directly after these hydrostatic Acalepha that we may place the 



DiPHYES, Cuv., 



A very singular genus, where two different individuals are always 

 found together, one encased in a cavity of the other, but susceptible of 

 being separated Avithout destroying the life of either. They are ge- 



* Such is the Physsophora hydrostatica , Gm. The individual named Phys. imiso- 

 nema, by Per., Voy. XXIX, 4, is well preserved; that of Forskahl, Ic., XXXIII, 

 E, e, 1, e, 2 ; Encyc.. LXXXIX, 7, 9, appears to be the same species, but deprived 

 of a portion of its tentacula, which are easily removed. I also think that the Phys- 

 sn2)honi rosacea, Forsk., XLIII, B, b, 2, and Encyc, LXXXIX, 10, II, is a muti- 

 lated specimen of another species. 



Add Rhizophysa Chamissonis, Eisenh., Medus., Ac. Nat. Cur. X, pi. 35, f. 3; — 

 Hhiz. hdianthus, and Uhiz. melo, Q,uoy and Gaym., Ann. des Sc. Nat., X.. pi. 5, and 

 many other undesciibed species. 



t Quoy and Gaym., An. des Sc. Nat. X, pi. 10, 4, A, f. 1 — 12. 



N.13. The Glebe of Otto, Ac. Nat. Cur., XI, p. II, pi. 42, f. 3, is merely a vesicle 

 of a Hippopus. 



+ Voy. de Freycin., Zool., pi. 87, f. 15. 



§ A new genus from the jMediterranean. 



II Physsophora filiformis, Forsk., XXXUl, F; Encyc, LXXXIX, 12 ; the same as 

 the Rhizophyza plancstoma, Per., Voy., XXIX, 3. MM. Quoy and Gaymard, how- 

 ever, think that these Rhizophyzse are merely Physsophora: which have lost their 

 lateral bladders. 



1 Stephanomia Amphitritis, Peron, Voy., XXIX, 5. The Slephanomia ta'am, 

 Lesueur, appears to me to appro.ximate nearer to Physsophora proper. 



