61] THE SKULL OF AMIURUS— KINDRED 61 



the anterior end of the suborbital lateral line canal of its side. The most 

 anterior dermal tubule of the canal issues from the bone through its dorso- 

 medial edge (Fig. 11). From the small central part of the bone four processes 

 radiate, two anterior and two posterior. The antero-lateral process is slender 

 and curves around the external margin of the anterior naris. The anterior 

 end of the suborbital canal, after leaving the main part of the bone at the 

 proximal end of this process, proceeds immediately to the external surface of 

 the head. The process is closely connected by ligament to the maxillary and 

 premaxillary bones, and to the ethmoid comu of the supraethmoid bone. 



The median anterior process of the lacrimal projects toward the middle 

 line of the fossa roof, posterior to the anterior naris. It contains the first der- 

 mal tubule of the suborbital lateral line canal, the pore of which lies lateral to 

 the pore of the first dermal tubule of the supraorbital canal, posterior to the 

 margin of the anterior naris (Fig. 11). 



The elongate median posterior process extends posteriorly toward the 

 anterior face of the ectethmoid bone. It lacks a lateral line canal element. 

 The anterior ossicle of the infraorbital series of lateral line canal bones (Fig, 

 15) is connected with its ventral margin by ligament. The lateral posterior 

 process of the lacrimal lies external to the first suborbital bone, so that the sub- 

 orbital lateral line canal enters the posterior margin of the lacrimal between 

 the posterior processes. After giving off the dermal tubule described above, 

 the canal ends by the passing to the exterior. There is one sense organ, the 

 most anterior of the suborbital lateral line canal, contained within the lacrimal 

 bone. The nasal bone encloses the most anterior sense organ of the supra- 

 orbital canal. 



The older writers — Cuvier, Stannius, Hallman, Wagner, Huxley and 

 others — recognized the lacrimal bone as the anterior element of the suborbital 

 or infraorbital series. In most of the forms studied it was the largest and 

 gradually came to have a greater morphological significance than the more 

 posterior elements of the series. It contains a part of the suborbital lateral 

 line canal in most teleosts and in Amia, and is usually related to tlie roof of 

 the nasal organ. Where its development has been studied (Schleip, 1903), 

 it has been found to arise primarily as an ossification developed in connexion 

 with a lateral line sense organ, and later has an osseous base formed from sur- 

 rounding connective tissue. In Amiurus, as noted above, the lateral line 

 element is the first to appear and the dermal part does not ossify until much 

 later. I am satisfied that this bone has two parts as Schleip has stated, and 

 that the dermal part may be homologized to the lacrimal bone of the higher 

 groups. As the lateral line canal is associated with those forms which live 

 in the water, so is the lacrimal canal found in those animals which pass most 

 of their lives in the air. In both cases the bone develops lateral to and usually 

 dorsal to the nasal organ and is a dermal ossification. It m.ay have more or less 

 connexion with the surrounding bones — nasal, maxillary, premaxillary, supra- 



