410 Mr. T. Davidson on the Brachiopoda. 



and ovaria resemble each other ; the zoosperms are in the shape 

 of a thread with a small head (fig. 10). Prof. Owen was likewise 

 able to observe the first commencement of the development of 

 the ova in the Lingula (fig. 15) ; the embryos, first of an ellip- 

 tical shape, form a stem a little later, without any change 

 having been efiected in the ulterior organization or develop- 

 ment. The embryos of the said Terehratula differ from this 

 very considerably (fig. 11); they resemble a Euastrum com- 

 posed of two unequal halves (for instance, the E. gemmatum or 

 ansatum, Focke) ; the rounded portion seems to be the anterior ; 

 the posterior part is a little wider, and is prolonged into two 

 points. What is the following development ? In none of the 

 ovaries observed by myself — for it is there that the embryo is 

 found — was the development more perfect. Considering our 

 total ignorance relative to the development of Terehratula^ every 

 observation must prove acceptable.'^ 



4. On certain calcareous Plates found in the mantle, oral arms, 

 and cirri of Terebratulina caput-serpentis. 



In the same paper, Prof. Schmidt observes, " that the mantle, 

 oral arms and cirri in Terebratulina caput-serpentis contain an 

 innumerable number of calcareous plates, generally flattened, 

 dilated and irregularly denticulated, situated in close vicinity 

 to each other, as seen in the examples figs. 12, 13 & 14. It is 

 easily conceived that these calcareous masses stiffen the parts 

 which contain them, and seem particularly to serve this func- 

 tion in the hollow cirri, thus preventing their sides from sinking 

 down. In the Norwegian Terehratula I examined they are not 

 to be found, nor have I obtained any in Terehratella dorsata; 

 but further investigation conducted on a larger number of 

 species will show whether they are or are not peculiar to the T. 

 caput-serpentis/' 



We may here mention that M. E. Deslongchamps has ob- 

 served a somewhat similar occurrence in his new species of Mor- 

 risia, for we find stated in a note he has added to my description 

 of Morrisia (French edition) : " Having placed in water during 

 several hours a Morrisia, which contained in its larger valve a 

 portion of its cirriferous arms, as well as their desiccated mem- 

 brane, we were able, after their immersion, to extend them more 

 than before : in placing these remnants under the microscope 

 we saw that they contained irregular scattered granulations 



to M. Loven, are the Ter. {RhynchowoWa.) psittacea, T. caput-serpentis, T. 

 cranium, and T. sepfigera. Mine answers better to T. septigera than to 

 the others, but it does not possess the charaeteristic septum in the smaller 

 valve." 



