752 B. W. KUNKEL 



its median side. At its anterior end the crista pterygoidea dis- 

 appears and the pterj^goideum extends forward as a small hori- 

 zontal process between the posterior end of the platinum laterally 

 and the fused trabeculae medially. Near the anterior end of 

 the lateral margin of the pterygoideum a conspicuous triangular 

 process — the processus ectopterygoideus — projects laterally be- 

 neath the distal end of the processus palatinus of the palato- 

 quadratum. Its posterior end lies with the crista pterygoidea 

 between the base of the processus pterygoideus of the palato- 

 quadratum laterally and the projecting antero-lateral margin of 

 the planum basale, coming to lie in close relation to the rudi- 

 mentary cartilago articularis {c.a., fig. 8). The body of the ptery- 

 goideum lies in a plane ventral to the planum basale, extending 

 laterally beneath the processus pterygoideus of the palato- 

 quadratum and medially beneath the processus basipterygoideus 

 to enclose from the ventral side a space in which run the ramus* 

 palatinus n. facialis and ramus communicans n. facialis cum 

 glossopharyngeo, as well as the arteria carotica interna, which lie 

 in the sulcus cavernosus on the median side of the crista ptery- 

 goidea. 



The palatinum {pal.) is a flat, triangular plate with its apex 

 directed posteriorly and base anteriorly. It lies at the same 

 level as the processus palatinus of the maxillare and occupies 

 the space in the roof of the mouth between the maxillare, vomer, 

 and pterygoideum. Its posterior end lies external to the ante- 

 rior prolongation of the pterygoideum and in front of the pro- 

 cessus ectopterygoideus. The plane of the palatinum is inclined 

 so that its median margin is somewhat dorsal to its lateral 

 margin. 



The parasphenoideum is wanting in the stage modelled, but 

 in an older embryo (carapace length, 13.5 mm.) it is present as 

 a small tripartite plate lying ventral to the region of the fenestra 

 hypophyseos. Its anterior median process extends as far for- 

 ward as the front margin of the fenestra while its postero-lateral 

 processes extend scarcely as far laterally as the lateral margins 

 of the fenestra. 



