Microscopica I Society. 3215 



arrangement of tubes was discovered. The shell is constructed on the inequilateral 

 plan of Truncatulina tuberculata, and viewed as an opaque object, exhibits a series of 

 vertical translucent spaces, with the intervening parietes to which the foramina are li- 

 mited. Along each of the vertical septal lines there exists an irregular double row of 

 very distinct pits or depressions ; similar pits are also seen inferiorly in the radiating 

 septa which divide the different segments of each convolution. On making a series of 

 sections of the shell, we learn that these pits or depressions are the external orifices of 

 a curious system of intraseptal canals and spaces ramifying in its interior. A section 

 taken close to the inferior flat surface of the shells exhibits a spiral translucent septum 

 separating the convolutions ; the segments present the ordinary foraminated aspect, 

 and are arranged in the usual spiral manner; in the radiating interseptal lines are 

 seen numerous small orifices, which open, by means of short canals, into the intersep- 

 tal spaces immediately above them. On making a second section, parallel to the first, 

 but a little above the peripheral margin, we perceive that there exists a number of 

 large branching intraseptal tubes and passages, which commence at the innermost seg- 

 ments, and proceed in a radiating manner towards the periphery ; these appear de- 

 signed primarily to multiply the number of external orifices ; but in addition to this, 

 they subsequently facilitate the establishment of a free communication between the 

 internal intraseptal spaces and those of the newer convolution, in which the septa are 

 more numerous. Small circular apertures appear along the course of these tubes, and 

 mark as many points where the section has traversed the orifices of the canals descend- 

 ing to the inferior surface of the shell. A third section, made parallel to the forego- 

 ing, is cut through the shell a little above the superior extremities of cells belonging 

 to the central convolutions. We here see that the portions which, in the former sec- 

 tions had the appearance of radiating lubes, are really the lower borders of vertical 

 interseptal spaces, but at the same time giving off true divergent cylindrical canals 

 from their external margins, which penetrate the thick parietes of the shell. Whilst 

 these spaces communicate externally, they open internally into a large irregular cavi- 

 ty, the true nature of which is better understood by reference to a vertical section of 

 this instructive object passing nearly through its centre; this section, if it has not tra- 

 versed the primordial cell, has certainly crossed the secondary one, along with four 

 others, in the successive order of their development. Whilst their inferior portions are 

 nearly on a uniform level, the upper extremities of those belonging to successive con- 

 volutions become rapidly elongated, leaving between them a large, irregular, conical 

 space. In the species under consideration, anew and curious feature is presented; 

 the cavities in the translucent calcareous shell are thickly lined with a dark olive-brown 

 substance : this substance not only exists in the interior of all the cells, but also occu- 

 pies the intraseptal spaces and their respective canals, as well as the irregular cavity in 

 the umbilical centre of the shell. It is most probable that this brown substance is 

 really the desiccated soft animal. A thin superficial section, made in the plane of the 

 oblique sides of the conical shell, exhibits some of the septa with the large orifices of 

 their interseptal canals, with the external parietes of some of the segments densely per- 

 forated with minute pseudopodian foramina, and a small lateral portion of the dome- 

 like apex of the shell, which is perforated with apertures, through which a free com- 

 munication is maintained between the external medium and the inclosed space. The 

 nature of the latter varies considerably ; sometimes it exists in the form of a large ir- 

 regular cavity, and at others as an intricate network of large canals. The character 

 of the external orifices also varies: in some examples they are large and patent ; in 



