1886.] "■*■ rstokes. 



still more different from those of 1. burmeisteri. The external incisors 

 are, on the other hand, more like those of the latter species in their trian- 

 gular form, though their inner angle is not produced as in that species. 



Explanation of Plate. 



The figures represent the Stereosterum tumidum in various pieces ; all of 

 the natural size excepting fig. 1, which is three-fourths natural size. 



• Fig. 1. The typical specimen on a slab of calcareous shale of the car- 

 boniferous formation ; the anterior part of the skeleton wanting ; viewed 

 from below, nc, notochordal canal exposed by the splitting of the verte- 

 bral centrum. 



Fig. 2. Vertebrse in a piece of weathered rock of darker color than the 

 slab. 



Fig. 3. A lumbar vertebra from the piece of matrix represented in fig. 

 2, anterior view ; a, inferior view 



Fig. 4. A caudal vertebra from the same piece of stone, left side ; a, in- 

 ferior side. 



Fig. 5. A dorsal vertebra with proximal portions of ribs embracing the 

 centrum ; from a different piece of matrix. 



Fig. 6. A vertebra of uncertain position, with descending processes, an - 

 terior view ; a, the same lateral view. 



Fig. 7. Humerus, the proximal portion represented by a mould ; from a 

 separate piece. 



Fig. 8. Coracoid bone from a separate piece. 



All the specimens are preserved in Museo National of Rio Janeiro, ex- 

 cepting that represented in fig. 1, which is in the collection of Madame 

 Ribeira de Andrada. 



Some new Hypotrichosis Infusoria. By Dr. Alfred O. Stokes. 



(Read before the American Philosophical Society, June 19, 1885.) 



Wet Sphagnum seems to be a favorite haunt for certain fresh-water pro- 

 tozoa. Dr. Leidy found it an unfailing source of supply for many of the 

 Rhizopoda, some of the most interesting forms described by that illustrious 

 naturalist being obtained from a little bunch of the moss. In my own 

 vicinage the beautiful plant is comparatively rare, but a single marsh of 

 not extended dimensions does happily exist here, with the pale Sphagnum 

 in some abundance greenly glimmering beneath the shallow water, while 

 the shadows of elder, azalea and serviceberry, and the broad leaves of 

 tangled smilax vines make the neighboring thicket dim and cool even 

 when the hot sun smites the furrowed field that borders it. Among these 

 pleasing surroundings the Rhizopoda are in numbers excelled only by the 

 Infusoria, as the following previously undescribed forms testify. And it is 



