180 AMERICAN JOURNAL 



during its passage through the gastro- genital mass. The 

 object of this arrangement appears to be the prevention of the 

 dragging of the nerve when the organ is distended with eggs. 



"Another remarkable arrangement is to be seen in the pas- 

 sage of the last portion of the intestine through the heart. At 

 the entrance of the intestine into the ventricle, there are mus- 

 cular bundles starting from the wall of the latter and inserted 

 perpendicularly into the wall of the digestive tube. At the 

 moment of contraction, these bundles must, by their shorten- 

 ing, tend to draw apart the walls of the intestine, which would 

 otherwise be compressed during the systole, and thus the 

 course of the fa?cal matters will not be interrupted. In these 

 large mollusks, the difference between the arteries and veins 

 is very easily seen ; the former have a very distinct double 

 epithelial and fibrous wall, whilst the latter are simple sinuses 

 hollowed out in the tissues. All the blood is compelled to 

 traverse an organ of haematosis (branchiae or mantle) before 

 returning to the heart. 



" The proper temperature of the animal, compared with that 

 of the bottom at which it lives, appeared to be rather high. 

 The temperature registered by thermometers sunk at the point 

 inhabited by the animals was about 63.°5 F. (17.°5 C). The 

 average temperature of the Tridacnse was 68. °5 F. (20° C.)." 

 — Annals and Magazine of Natural History, XVI., No. 95. 

 November, 1865. (From Comptes Eendus, October 9, 1865.) 



On the Correct Application of Certain Terms used in 

 the Description of Shells. By Augustus A. Gould, 

 M.D. 



"Taking a common clam for an example, and placing it 

 with the beak uppermost, he showed the position of the en- 

 closed organs, and that the extremity which was in front du- 

 ring locomotion should be called the anterior, and the opposite 

 the posterior extremity ; that the distance from the beak to the 

 opposite margin should be called the altitude, the distance 

 from the anterior to the posterior extremity the longitudinal 

 diameter, and the distance through from one valve to the 

 opposite the transverse diameter ; that the concentric markings 

 of growth should be called longitudinal, in distinction from 

 those which radiate from the beak, to which the name of ver- 

 tical should be applied. The terms equilateral, posterior side, 

 and anterior side, as used, he showed to be peculiarly impro- 

 per, and suggested instead the terms equi partite, posterior part, 

 segment or section, etc. Passing then to the common spiral 

 shells through the medium of Limax, Patella, Dentalium, and 



