94 BULLETIN OF THE 



orljit, five or six long tubules reach toward the anterior border. The orbital 

 goes down at the side of the rostral, not half-way from the skull to the end of 

 the snout. Nearly or quite all of the tubules on this surface are branched. 



On the lower aspect the pleurals pass toward the front margin, and, running 

 parallel with it, send out a number of simple tubules; afterward, along the 

 middle of the fin, they take a course of some directness to the posterior exten- 

 sion of the jugular, a little distance forvvard from the pelvis. A single tubule 

 marks the turning point. Bending around and back, as far as tlie mouth, in 

 a waved course, the suborbitals make a long loop forward. Behind this loop 

 they extend toward the gill apertures; in front of the latter they turn toward 

 the nostrils and meet the subrostrals opposite the mouth. The orbito-nasals 

 are of medium length, the nasals are long and moderately curved, tlie median 

 is short, and the prenasals are elongate and close together. Between the nos- 

 trils each subrostral makes a deep bend, on the nasal valve; they end, at the 

 side of the prenasals, in a series of rings or capsules connected with each other 

 by thin transparent tissue, which only near the mouth presents the semblance 

 of a tube. These rings are closed follicles, which do not appear to be con- 

 nected with the surface; they seem in most resjjects identical with the folli- 

 cles of Savi, and trace their origin to obsolescent canals, of which portions 

 surrounding certain nerve endings have persisted and become closed sacs. 

 Rings and enlargements also are seen ia the front portions of the prenasals. 

 On each side of the symphysis, near the teeth, a crooked oral reaches about 

 half-waj' to the first gill cleft. A short sternal crosses the middle in front of 

 the pelvic spine. 



Distinguishing peculiarities appear in the presence of both pre- and post- 

 scapulars, in the isolation of the subrostrals, in the groups of tubules on the 

 front sections of the ventro-pleurals, and in the oddly shaped loop in the 

 suborbitals. 



Disceus. 



Disceus strongylopterus (Plate XXXV.). One of the most peculiar canal 

 arrangements to be found in the order occurs in this genus. Pre- and post- 

 scapulars are both present, and, outside of the prominent scapular curve in the 

 laterals, there is a pre- scapular area included by the pre-scapulars. The post- 

 scapulars are short ; by uniting among themselves or their branches they form 

 an irregular plexus. First passing back from the laterals, the pleurals then 

 turn forward at a sharp angle, and, in their course through the middle of the 

 pectorals, send toward the margin a large number of long tubules, each of 

 which bears a small group of branchlets at its end. Connecting with tlie orbi- 

 tals by means of^a couple of tubules, the ]deurals bend back toward the fore- 

 head, whence they run forward a little more than half the distance to the tip 

 before descending. 



The aural is long and transverse. Starting outward from the aural, the 

 elongate occipitals turn forward, after sending out the occipital branches. In 



