31] THE NASAL ORGAN IN AMPHIBIA—HIGGINS 31 
throughout the entire urodelan order, as primitive, would be unjustified; 
but, the greatly retarded process of chondrification, the absence of cristae 
and cornua trabeculorum, together with the entire separation of the roof 
of the capsule from the other parts, may be explained in either of two 
ways; Necturus has either descended from some more specialized Urodele, 
or, as the retarded process of chondrification would suggest, it may repre- 
sent a neotenic condition of some form, like Spelerpes. 
AMPHIUMA MEANS 
The first of the three capsules of Amphiuma studied, is that of a larva 
still within the egg, in which the chondrocranium is very incomplete, 
resembling in many ways the larva described by Kingsley (1892), and 
figured by Winslow (Fig. 18, 1898). 
Each trabecula, from the crista forwards, inclines, at first gradually, 
and then somewhat more abrupt, toward the median line; the two uniting 
to form a small rectangular planum basale (pd, Fig. 29), which supports 
the olfactory lobes. Anterior to the planum, each trabecula’ continues 
forward a short distance, and then expands into a triangular cornu, concave 
upon its dorsal surface to support the anterior part of the olfactory sac. 
The cornua are separated from each other by a deep and narrow inter- 
nasal space, resembling that of Spelerpes, the Urodele, the larva of which 
most resembles the early Amphiuma. 
The cristae trabeculorum (cr f) are well developed and extend forward 
to the base of the antorbital process (pa), which in Amphiuma is directed 
obliquely forward from the trabecula, rather than at right angles to it as in 
other Urodeles. The anterior margin of each crista trabeculae is con- 
tinued forward as a cylindrical bar along the medial dorsal margin of the 
nasal sac. At the level of the anterior end of the antorbital process, the 
bar runs forward and outward and passes obliquely over the nasal organ, 
giving rise to a short process just dorsal to the nasal sac, and continuing 
outward and downward to the lateral surface of the sac where it turns 
directly forward and runs along the lateral surface of the sac nearly to the 
level of the planum basale. Hay (1890) speaks of this bar as the rudi- 
mentary nasal capsule, while Winslow (1898) describes it as projecting 
forward, outward and downward, but without the small dorsal processes 
present in my stage, and which help to explain the later modifications of 
the capsule. In its origin from the trabecular crest, this bar, which 
probably contains elements of both ethmoidal column and tectal cartilage, 
recalls the process in Spelerpes, extending forward from the anterior margin 
of the crest, which was interpreted as the posterior end of a developing 
columna ethmoidalis. 
Olfactory foramina do not exist, but each olfactory nerve passes over 
the trabecula just in front of the crista trabeculae, where the nasal organ 
and the olfactory lobe are very close together. 
