Figure 64.— External features of other 



representative balistid genera : Odonua niger— 



upper left, scale plates of the tympanum 



region just behind the gill slit and above the 



pectoral fin base; upper middle, 



scales from upper middle region of body, 



including lateral line canal bearing scales; 



upper right, ventral view of encasing 



scales at end of pelvis (anterior to left), 



with arrow indicating major region of 



fiexibility (two terminal branches of 



modified fin-ray element protrude posteriorly); 



lower left, nasal region as 



seen externally (above) and the olfactory 



lamellae as seen with the top of the 



nasal sac removed. 



species, and room for about seven abdominal vertebrae, 

 also as in Recent species, although only the last four ab- 

 dominal vertebrae can be seen relatively clearly. There 

 appear to be about 12 caudal fin rays in a slightly round- 

 ed fin. There is a well-developed supraneural strut sup- 

 porting the rear end of the carina. The basal pterygio- 

 phores that are best shown, anteriorly in the soft dorsal 

 fin, have well-developed lateral flanges. The form and 

 number of the teeth do not show. The stout pelvis has a 

 small but distinct dorsal lobe posteriorly. The scales, 

 best seen posteriorly on the body, bear one or more low 

 longitudinal ridges along the basal plate, those in the 

 region of the caudal peduncle being larger and longer 

 than elsewhere and oriented in longitudinal rows, just as 

 in many Recent species. 



An additional specimen from the black schist of Can- 

 ton Glarus, NSKG 178b, 119 mm SL, can be assigned to 

 Balistomorphus oualis, mainly on the basis of its slender 

 body, the depth between the soft dorsal and anal fin 

 origins being about 36 mm (30% SL). It is a poor impres- 

 sion that at one time was in counterpart, but the head to 

 the right plate (presumably numbered 178a) cannot be 

 found. The caudal peduncle depth is 12.4 mm (10.4% 

 SL). The first dorsal spine is 22.8 mm (19.2% SL), the 

 second 9.5 mm (8.09; SL), and the third 5.1 mm (4.3% 

 SL), all of which measurements are compatible with that 

 of the holotype of B. oualis from the same strata, as are 

 the well-developed supraneural strut supporting the car- 

 ina and the approximately 11 caudal vertebrae. Little 

 else of interest can be seen. 



Balistomorphus spinosus (Agassiz 1842 illustration, 

 1844b description) is a moderately deep bodied species. 

 The holotype, and only relatively complete specimen 

 available, BMNH P. 3973, a single impression (head 

 right) is 92.0 mm SL. The depth of the body between the 

 soft dorsal and anal fin origins is 46.0 mm (50% SL). The 

 least depth of the caudal peduncle is 12.2 mm (13.3% 

 SL). The length of the first dorsal spine, which bears low 

 asperities laterally, is 21.0 mm (22.8% SL). The second 

 dorsal spine cannot be measured, but the third spine is 



5.0 mm (5.4% SL). The vertebral column can be inter- 

 preted either as 7 + 11, as in Recent species, or as 8 + 10. 

 The caudal fin appears to have 12 rays. There is a well- 

 developed supraneural strut supporting the rear end of 

 the carina. The basal pterygiophores have well- 

 developed lateral flanges. The form and number of the 

 teeth do not show. There is a slight indication that the 

 stout pelvis had a low dorsal lobe posteriorly. The scales 

 are not as well indicated as in B. oualis, but low granula- 

 tions of some sort were present on the basal plates. The 

 anal fin base seems to have been substantially shorter 

 than the soft dorsal fin base, more so than in B. oualis. 



An additional specimen from the black schist of Can- 

 ton Glarus, NSKG 189a and b, which is too poor an im- 

 pression in counterpart to accurately measure, can 

 probably be assigned to B. spinosus on the basis of its 

 moderately deep body, as can another not listed in the 

 material examined (BMNH P. 1819) from the same 

 strata whose bones are too disorganized to measure. 

 These additional specimens add little to our knowledge 

 of the species, except that the first dorsal spine in one of 

 them bears even better developed asperities laterally, 

 and apparently anteriorly, than does the holotype of B. 

 spinosus. 



Balistomorphus orbiculatus (Heer 1865, see also 1876) 

 is an extremely deep bodied species. The holotype, and 

 only known specimen, NSKG 2688, a single impression 

 (head left), is 65.6 mm SL. Heer's illustration of the 

 specimen shows the head facing right, so either the illus- 

 tration was reversed or, less likely, the specimen was 

 originally in counterpart and only the head to left half 

 remains in the Glarus collection. Woodward (1901:568) 

 believed the great depth of the specimen to be due to dis- 

 tortion, but, as with the other specimens of Balistomor- 

 phus (and of the Oligocene triacanthid Acanthopleurus, 

 which see) from the black schist of Canton Glarus, the 

 neural and haemal spines of the vertebrae have a normal 

 relationship with the basal pterygiophores of the soft dor- 

 sal and anal fins and the patterns of the scales are nor- 

 mal, neither of which would be the case if B. orbiculatus 



