GENUS TINTINNIDIUM. 6ll 



while homogeneous, is transversely annulate ; and a fourth for such as 71 ventricosus, 

 in which the test is coarsely granular but not annulate. So far, indeed, as the granular 

 consistence of this excreted element is concerned, it is without doubt dependent 

 to no small extent upon surrounding conditions, such as the clearness or turbidity 

 of the waters which the animalcules inhabit. 



GENUS II. TINTINNIDIUM, S. K. 

 (Tintinnus ; oidos, form.) 



Animalcules ovate or pyriform, resembling those of the genus Tintinnus, 

 but excreting a sheath or lorica, usually of a mucilaginous consistence, 

 which is permanently affixed to foreign objects. Inhabiting salt and fresh 

 water. 



This new genus is here instituted for the reception of the Tintinnus inquilinus, 

 in part, of Ehrenberg, and the Tintinnus fluviatilis of Stein two forms closely 

 allied to one another, and which differ from the typical representatives of the last- 

 named genus in their essentially sedentary habits. 



Tintinnidium marinum, Ehr. sp. PL. XXXI. FIG. 9. 



Lorica transparent, subcylindrical, two and a half to three times as long 

 as broad ; animalcule when retracted filling two-thirds of the cavity of the 

 lorica, projecting beyond its orifice, when extended, to a distance of one- 

 half of its total height ; retractile pedicle in full extension equal in length 

 to the body, sometimes attached to the bottom and sometimes to one side 

 of the inner surface of the lorica. Length of lorica 1-240". 



HAB. Salt water, attached to various marine algae. 



The above specific title is here associated with that variety of the so-called Tintin- 

 nus inquilinus met with by Ehrenberg attached to algae at Kiel, and as figured by 

 him at pi. xxx. fig. ii. i and 2, of his ' Infusionsthierchen.' This animalcule is 

 altogether distinct from the typical free-swimming representatives of the species first 

 described by Schrank, and as also encountered by Ehrenberg in the harbour of 

 Copenhagen. Its possible identity with the Tintinnus mucicola of Claparede and 

 Lachmann, delineated at fig. 16 of the same plate, is adverted to in the description 

 given of that species. 



Tintinnidium fluviatilis, Stein sp. PL. XXXI. FIG. 8. 



Lorica cylindrical, transparent, mucilaginous, surface uneven, frequently 

 with incorporated foreign particles ; body of animalcule conical or campanu- 

 late, occupying about one-half of the cavity of the lorica, projecting when 

 extended to nearly one-half its length beyond its aperture ; retractile 

 pedicle attached to either the side or the bottom of the cavity of the lorica ; 

 contractile vesicle spherical, subcentral ; endoplast elongate-ovate, laterally 

 located, having attached to it a minute, round endoplastule. Length of 

 lorica 1-200". HAB. Fresh water, on aquatic plants. 



With the exception of its fresh-water habitat, this species seems to differ very 

 little from the form previously described. In addition to its observation by both 

 Stein and Claparede and Lachmann, the present author has received drawings of 

 an apparently identical form through Mr. Thomas Bolton, the originals of which 



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