596 



PISCES. 



[DIN. — ECT. 



tiimidus, St. John &. Worthen, 1875, Geo. 

 Sur. 111., vol. 6, p. 339, St. Louis Gr. 

 Dinichtjiys, Newberry, 1873, Ohio Pal., 

 vol. 1, p. 313, and vol. 2, p. 3. [Ety. 

 deinos, terrible; ichthys, a fish.] Cranium 

 composed of thick bony plates, strength- 

 ened with internal arches anchylosed 

 together, occipital bone in the type 

 species three inches in thickness; rel- 

 atively small maxillaries bearing a 

 number of acute, conical, anchylosed 

 teeth, which interlocked with a similar 

 series on the mandibles; premaxillaries 

 large, strong, triangular plates or teeth; 

 mandibles of great length, flattened and 

 spatulate behind, turning up anteriorly 

 to form a strong triangular tooth, with 

 its fellow of the opposite mandible, 

 interlocked with the great, divergent, 

 premaxillary teeth; vital parts of the 

 body covered with large, thick plates 

 which formed a carapace. Type D. 

 terrelli. 



hertzeri. Newberry, 1873, Ohio Pal., vol. 

 1, p. 310, Portage Gr. 



Fia. 1120 



i iivs hertzeri. 



terrelli, Newberry, 1873-75, Ohio Pal., 

 vol. 1, p. 313, and vol. 2, p. 3, Por- 

 tage Gr. 

 Diplasi'IS, Matthew, 1888, Can. Rec. Sci., 

 vol. 2, p. 251. [Ety. diplos, double; as- 

 pis, shield.] Small, having plates on 

 the head, back, and sides, and one ven- 

 tral plate ; plates bearing very fine 

 ridges. Type D. acadica. 



acadica, Matthew, 1888, Can. Rec. Sci., vol. 

 2, p. 251, Up. Silurian or Low. Devo- 

 nian. 

 Diplodus, Agassiz, 1843, Recherches sur les 

 Poissons Fossiles, t. 3, p. 204. [Ety. 

 diploos, double ; odous, a tooth.] This 

 name was used by Rafinesque for a 

 genus of Sparidie in 1810, Indice d'Lit- 

 tologia Siciliana. Teeth having a flat- 

 tened or rounded base, from which 

 spring two lateral and sometimes a 

 small central denticle ; each jaw bore 

 several hundred teeth in radiating rows, 

 the points projecting inward. They 

 belong to sharks possessed of spines, 

 described under the names of Oracan- 

 tlius and Xenacanthus. Type D. gib- 

 bosus. 



acinac* s, Dawson, 1860, Acad. Geol., p. 

 211, and Can. Nat. Geol., vol. 5, Coal 

 Meas. 



compressus, Newberry, 1857, Proc. Acad. 

 Nai.Sci. Phil., vol. 8, p. 99, and Ohio 

 Pal., vol. 1, p. 335, Coal Meas. 



duplicates, see Thrinacodus duplicatus. 



Fig. 



11J7.— Dlplodua 

 latus. 



DlPTKKBS, Sedgwick 

 Geo. Trans., 2d 



miL 



gracilis, Newberrv, 1857, Proc. Acad. Nat. 

 Sci. Phil., vol. 8, p. 99, and Ohio Pal., 

 vol. 1, p. 385, Coal Meas. 



incurrus, see Thrina- 

 codus imurvus. 

 latus, Newberry, 1857, 

 Proc. Acad. Nat. 

 Sci. Phil., vol. 8, p. 

 9!), and Ohio Pal., 

 vol. 1, p. 336, Coal 

 Meas. 

 penetrans, Dawson, 

 1800, Acad. Geol,, 

 p. 211, and Can. Nat. 

 and Geol., vol. 5, 

 Coal Meas. 

 & Murchison, 1885, 

 ser., vol. o. [Ety. 

 <li/ l (cr(»i, two-winded.] Diptera is an 

 order of insects established by Linn.ius. 

 Small fusiform fishes ; heads com- 

 pressed, tails heterocercal ; two dorsal • 

 fins opposite two simi- 

 lar anal fins, the 

 second of each the 

 larger ; a strongly 

 marked lateral line ; 

 scales circular, thickest 

 in the middle, vari- 

 ously curved with con- 

 centric lines or longi- 

 tudinal ridges. Type 

 D. brachypygopterus. 

 sherwoodi, Newberry, 

 1875, Ohio Pal. vol. 2, 

 p. 61, Catskill Gr. 

 Drepanacantiius, Newberry it Worthen, 

 1866, Geo. Sur. 111., vol. 2, p. 120. [Ety. 

 drepatie, a sickle; akantha, spine.] Fin 

 spines compressed laterally, gradually 

 tapering to an acute point, curved for- 

 ward; anterior margin with a row of 

 flattened or conical tubercles ; lateral 

 surfaces with tubercles in longitudinal 

 rows; posterior margin without hooks, 

 sometimes with tubercles. Type D. 

 gemmatus. 

 ancrps, see Xystracanthus anceps. 

 gemmatus, Newberry & Worthen, 1866, 

 Geo. Sur. 111., vol. 2, p. 123, Keokuk Gr. 

 reversus, St. John& Worthen, 1875, Geo. 



Sur. 111., vol. 6, p. 456, St. Louis Gr. 

 stellatus, see Batacantbus stellatus. 

 Ectosteorachis, Cope, 1880, Pal. Bull. No. 

 32, p. 19. [Ety. ektos, without ; osteon, 

 bone ; rachis, a ridge, backbone.] Base 

 of the skull consists of ossified para- 

 chordals, which embrace the chorda 

 dorsalis posteriorly, and are continued 

 for a short distance posteriorly as a 

 tube; anteriorly the chordal groove is 

 open ; trabecular not ossified ; cranial 

 structure embryonic ; above and in 

 front of the opening for the chorda the 

 neural canal enters the groove ; para- 

 chordals subtriangular. TypeE. nitidns. 

 ciceronius, Cope, 1883, Pal. Bull. No. 36, 

 in Ptoc. Am. Phil. Soc, p. 628, Per- 

 mian. 



Fig. 1128.-Dipte- 

 ru8 sherwoodi. 



