. Bulletin. Natural history. A PRIMITIVE DEVONIAN LUNGFISH 73 (Fig. 29B; Figs. 74 and 75) merges with the lateral nasal wall to form the thick pos- terodorsal corner of the nasal capsule. The posterior wing of the flange reaches dor- sally and posteriorly and forms a stout buttress under the inner surfaces of bones "O" of the dermal skull roof and the lateral margin of a deep recess extending for- ward from the orbital chamber. Dorsally the postnasal wall is continued as a thin lamina of bone that joins the posterior margin of the tectum nasi. This lamina is perforated by a large for
. Bulletin. Natural history. A PRIMITIVE DEVONIAN LUNGFISH 73 (Fig. 29B; Figs. 74 and 75) merges with the lateral nasal wall to form the thick pos- terodorsal corner of the nasal capsule. The posterior wing of the flange reaches dor- sally and posteriorly and forms a stout buttress under the inner surfaces of bones "O" of the dermal skull roof and the lateral margin of a deep recess extending for- ward from the orbital chamber. Dorsally the postnasal wall is continued as a thin lamina of bone that joins the posterior margin of the tectum nasi. This lamina is perforated by a large foramen for the profundus V nerve (Figs. 29A, c prf). In one specimen (18815) this profundus canal divides and two foramina—a large ventrolateral one and a small dorsomedial one—are found on the anterior surface of the postnasal wall. Apart from that for the profundus, the only canal to pierce the postnasal wall is fairly wide and opens posteriorly through the ventral surface of the distal part of the wall. This canal (Fig. 29A, cm V) is directed dorso- medially and enters the nasal cavity just lateral to the anterior opening of the profundus canal. Possibly it carried a r. maxillaris V or a portion of the profundus lateralis V. Orbital Region. Details of the external structure of the endocranium in the orbital region are revealed in specimen F 10813A; certain details of the passage of canals through the endocranial wall are revealed in the incomplete specimen P 33699, which has already been shown to indicate a great deal of the structure of the palatal region. From these specimens, and from X-ray photographs of specimen 18815, an almost complete picture has been built up of the structure in the orbital region (Figs. 31, 32). It lacks only detailed information concerning the shape of the endocranial cavity in this region. The orbital region of the endocranium is here defined somewhat arbitrarily as the portion of the skull posterior to the postnasal wall and anterior to the tr
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