distal one-fifth of the length the tooth is strongly con- 

 stricted into a blunt nipple. In the distal halves of their 

 lengths the teeth bear about 10 annularlike rings, which 

 I doubt are artifacts. In the upper jaw, grooves represent 

 where teeth once were present, and perhaps of their 

 sockets. More than 20 pharyngeal teeth are present in the 

 region in front of the pectoral fin base, these being 

 similar to those of the jaws but much smaller, the largest 

 being about 0.5 mm (0.5% SL) long. 



The body bears numerous, mostly isolated, scale 

 plates of moderate size. Each plate has a strong rela- 

 tively high central spine peripheral to which are much 

 smaller and lower rounded bumps or granulations similar 

 to those of Protobalistum. The more or less isolated 

 plates, which probably covered only about one-fourth of 

 the surface of the body, seem to become more numerous 

 ventrally, where they may have been placed in more or 

 less regular horizontal rows, with some contact between 

 individual plates. The plates are largest and most 

 regularly arranged along the ventral edge of the body 

 from the region of the branchiostegals posteriorly to the 

 anal fin base, the largest plates being in the abdominal 

 area. The largest plates have a diameter of about 5.0 mm 

 (4.8% SL). Very few scale plates are evident on the head. 



the only one clearly seen being on the profile of the snout 

 about midway between the mouth and eye. The scale 

 covering of Spinacanthus is comparable to that found on 

 Protobalistum anterior and posterior to its carapace of 

 articulated hexagonal plates. 



The anatomical features of the Eoplectinae, recently 

 described by Tyler (1973b), are summarized briefly 

 below. 



The Eoplectinae are represented by two species known 

 only from their holotypes, only one of which (Eoplectus) 

 is well preserved. 



In most of its features Eoplectus bloti Tyler (1973b) is 

 a generalized plectognath at the triacanthodid level of 

 organization. It has at least five and probably six dorsal 

 fin spines, a rounded caudal fin of 12 rays (i, 10, i), a 

 generalized caudal skeleton, a short caudal peduncle, 

 and the most generalized condition of the pelvic fin 

 known among the plectognaths, this being a spine and 

 four well-developed branched rays. The overall con- 

 figuration of the body is also triacanthodid. However, 

 Eoplectus has the jaws and dentition modified into a 

 crushing beak, with numerous small rounded dental 

 units incorporated into the matrix of the premaxillary 

 and dentary. This condition otherwise is found among 



Figure U .—Eoplectus bloti: lateral view of holotype, 

 65.2 mm SL, Eocene of Monte Bolea, Italy. 



