890 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY, 



with the propyloric ossicle, it bears the large blunt 

 median tooth (med. t.) on its ventral surface. 



The Propyloric Ossicle (pr.p.) is a small median plate 

 situated almost vertically. When the gastric mill is at 

 rest the lower end of this ossicle is considerably behind 

 its upper end. Its upper end articulates with the front 

 portion of the pyloric ossicle, and its lower end is in 

 contact with the posterior end of the urocardiac ossicle. 

 The plate is roughly triangular in shape and its apex, 

 which points downwards, is bifurcated. The base of the 

 triangle is dorsal and is extremely concave. The ossicle 

 is highly calcified around the edges, but in the centre it 

 is almost membranous. 



The Pyloric Ossicle (o.%>y.) is a median ossicle lying 

 between the two exopyloric ossicles which articulate with 

 it at each side. It covers the anterior part of the p}doric 

 region of the stomach. Its central portion is membranous, 

 but laterally it is slightly calcified. These lateral 

 calcifications indicate that the pyloric ossicle is really a 

 paired structure. In the Macrura all signs of the double 

 origin disappear. 



Cardiac "Supporting Ossicles.' 5 

 The Pectineal Ossicles (pec.) are a pair of irregular 

 hammer-shaped ossicles, each lying in the lateral wall of 

 the fore-gut beneath the posterior portion of the 

 zygocardiac ossicle. The curved " handle " of the hammer 

 points anteriorly. On the inner side of the " head " of the 

 hammer are three claw-like teeth. These are the lateral 

 accessory teeth (a.t.l.). [" Infero-lateral cardiac teeth,'' 

 Huxley.] 



The Prepectineal Ossicles {p.peo.) are a pair of long 

 narrow rod-like ossicles, each being concave on its inner 

 border and extending upwards from the pectineal ossicle 



