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VISION 



Figure 26 Dorsal view of the acousticolateralis area and brain stem in (A) Squalus and 

 (B) Mustelus; the caudal half of the cerebellar corpus is removed to show details of the 

 auricle, alll, anterior lateral-line lobe; alln, anterior lateral-line nerve; ar, anterior ramus of 

 statoacoustic nerve; c, corpus of cerebellum; dr, dorsal root of anterior lateral-line nerve; 

 g, granular cap of anterior lateral-line lobe; 11, lower leaf of auricle; mlf, medial longi- 

 tudinal fasciculus; pill, posterior lateral-line lobe; plln, posterior lateral-line nerve; pr, 

 posterior ramus of statoacoustic nerve; ul, upper leaf of auricle; vr, ventral root of 

 anterior lateral-line nerve; IX, glossopharyngeal nerve; X, vagal nerve. 



The acousticolateralis area of the medulla can be divided grossly into 

 anterior and posterior lateral-line lobes (Figures 8, 9, 12, 13, 16, 17, 26). 

 Considerable variation occurs in the development of these lobes in cartila- 

 ginous fishes. Squalomorph (Figures 9, 26 A) and squantinomorph sharks 

 are characterized by moderately developed lobes, whereas chimaeras and 

 galeomorph sharks show marked enlargement of both lobes with strongly 

 hypertrophied anterior lobes (Figures 8, 12, 13, 26B). Batoids do not exhibit 

 as much variation as sharks, but their level of lobe organization is most 

 similar to that of the galeomorph sharks (Figures 16, 17). 



In all cartilaginous fishes the lateral and dorsal surfaces of the anterior and 

 posterior lobes consist of a neuropil layer, composed of unmyelinated axons 

 and a few stellate cells, which is termed the cerebellar crest (cc, Figures 

 21-23). Large Purkinje-like cells, deep to the cerebellar crest in each lobe, 

 send dendrites into the crest neuropil (Larsell 1967). In Scyliorhinus, the 

 dendrites of the Purkinje-like cells entering the crest are covered with spiny 



