9T2 MR. J. H. LLOYD AND MiSS EDITH SHEPPARD ON 



matter of some difficulty, as the connective tissue had hardened 

 to an extraordinary extent and the cartilage had become exceed- 

 ingly brittle. We hope later to publish an account of the 

 structure of the visceral arches, limb-girdles, vertebral column, 

 and fins. 



A description of this fish appears to be desirable as, with the 

 exception of the external characters, we have not been able to 

 find any consecutive account of its anatomy. 



Both Garman (4) and Day (3) have given a species definition 

 and figured the entii-e animal, the former including it in the 

 genus CestraGion under the name of Cestracion zygcena Linn. 

 Gegenbaur (5) gives two figures of the head and briefly mentions 

 the species in his text, but our observations do not agree with his 

 in all respects. The macroscopic structure of the brain has been 

 briefly described and figured by Busch (3) and Miklucho-Maclay 

 (12). 



Skull. 



The cranium bears at its anterior end a stout rostrum which 

 consists of three bars. Two of these {d.r.) arise from the dorsal 

 surface and run forward and downwards to unite with a median 

 ventral bar (v.r.). The latter is expanded anteriorly to form a 

 small flattened plate, which is perforated by a single small 

 foramen. We were unable to find any trace in our specimen of 

 the rostral appendages (' Anhang der Rostrum') figured by 

 Gegenbaur (5). 



At the anterior end of the cranium is a large fontanelle (a.f.) 

 extending from between the two dorsal bars of the lostrum to 

 the ventral bar of the rostrum. This fontanelle, which therefore 

 occupies the whole of the anterior end of the cranium, is completely 

 covered by a strong sheet of fibrous connective tissue. 



When seen from the dorsal surface (text-fig. 2) the most 

 prominent features of the skull are the large, lateral, wing-like 

 expansions of the olfactory regions (o.c). These expansions are 

 dorso-ventrally compressed, and their distal extremities taper 

 almost to a point. The orbits (o.) are situated immediately 

 posterior to the distal portion of the capsules. 



The depression into which the 2nd to 7th cranial nerves emerge 

 in a normal skull also bears the eye, and is therefore the orbit. 

 In Zygcena malleus the orbit is a separate structure, and we have 

 therefore decided to call the depression into which the above 

 mentioned cranial nerves emerge the pre-a,uclitory depression 

 {p.a.d.). This has resulted in a few other changes in the nomen- 

 clature of related parts, but it appears preferable to us to do this 

 rather than to retain terms which give incorrect impressions of 

 the relationships of the regions to one another. 



The orbit is composed of a post-olfactory process (p-o.) which 

 runs backwards and outwards from the olfactory capsule to form 

 the anterior three-quarters of the circumference of the orbit on 

 the dorsal surface. The orbit is completed dorsally by a bar of 



