298 Morbid Influence of the Spinal Nerves. 
cases and experiments which tend to prove that pain and disor- 
ganization, as well as impaired function and paralysis, are con- 
sequent on causes which interrupt the due transmission of 
nervous influence to the affected parts. It has been very justly 
remarked that nature is sparing of causes, but profuse of effects. 
I am, Sir, 
Your very obedient Servant, 
Malmsbury, R. P. Prayer. 
Dec. 4, 1822. 
Art. V. Lamarcx’s Genera of Shells. 
(Continued from page 86.) 
2. Mactra *, 
Shell transverse, inequilateral, subtriangular, rather gaping 
at the sides; beaks prominent. One compressed grooved car- 
dinal tooth, on each valve, and, near it, a pit, extending in- 
wards. Two compressed, entering +t, lateral teeth, near the 
hinge. Ligament internal, inserted in the cardinal pit. If the 
pit be very large, the cardinal tooth is very oblique, short, and 
even partly obliterated, but the lateral teeth always exist. 
Type. Mactra gigantea}. 
Shell, large, solid, whitish-yellow, transversely substriated ; 
gaping within the nates; cardinal pit, very large, cordate. 
33 species. South American Seas. Pl. v. Fig. 32. 
3. Crassatella §. 
Shell inequilateral, suborbicular or transverse; valves close. 
Two subdiverging cardinal teeth, with a pit by the side of them. 
Ligament internal, inserted in the pit of each valve. Lateral 
teeth, none, or obsolete. 
The crassatella is distinguished from the mactra and lutraria 
by the valves, when shut, being quite close on both sides. In 
* Mactra, a kneading trough. 
+ Intrantes, when the hinge teeth of the opposite valves take into each 
other, like the cogs of acouple of wheels, they are called intrantes, entering. 
$ Gigantic. § From crassus, thick. 
