SYNECHODUS. 219 



with several feebly marked lateral denticles on each side, and a gently arched 

 base-line (PL XLV, fig. 7 h). ISuch teeth may perhaps belong to the opposing jaw ; 

 but whether this be so, or whether one type of front tooth characterises the male, 

 the other the female, still remains to be determined. 



The vertebral centra are well calcified, and those in the anterior part of the 

 fish (PI. XL VI, fig. 2) are slightly deeper than long. The foremost centrum (1) is 

 indeed especially short, and appears solid in two specimens; but the other centra 

 are clearly asterospondylic. Each half of the pectoral arch (^tct.) consists of a 

 single, slender cartilage, produced upwards into an attenuated extremity, and very 

 similar in shape to the corresponding element both of rahvusinnad; and of 

 Hijhodns. 



Traces of shagreen are often observal)le in the fossils. Some grannies are 

 smooth and (juadrate in shape, but most are more or less oval, ridged and grooved 

 in the direction of their long axis (PI. XLVI, fig. 2 (/). All have a deep base of 

 insertion. 



ILifhoiis and Jjoraltlics. — Zone of lfi)lader fjnlxjlohosns : Dover and Burham, 

 Kent; Glynde, Sussex; near Ciimbridge. Zone o1i fSclducnhaclua cai-ians: Dover. 



2. Synechodus nitidus, sp. nov. Plate XLVI, figs. 3, 4. 



Ti/2)('. — Imperfect jaws with teeth from zone of llulader subijJohusuif ; British 

 Museum. 



iSpecijic Clianidcrs. — Somewhat larger than the type species; the large anterior 

 teeth completely smooth, with more slender lateral denticles ; the principal antero- 

 lateral teeth also remarkably smooth, only feebly marked with fine vertical wrinkles, 

 not reticulations, at the base of the crown, which is always continuous ; hindmost 

 teeth with low but sharply pointed cusps, also marked with vertical wrinkles, not 

 reticulations. 



Dcftcriptlon of Hj't'ciiiieiis. — The remains of the jaws in the type specimen show 

 that they nmst have attained a length of about 12 cm. With them are a few 

 scattered teeth both from the front and from the hinder region. The large front 

 teeth (PI. XLVI, fig. 3 a) are completely smooth, with a slightly arched coronal 

 base-line, a slender principal cusp, and not more than four well-separated, acumi- 

 nate denticles on either side. Their root is coarsely crimped at the outer border, 

 and forms a large, rounded prominence beyond the crown inwards. One of the 

 antero-lateral teeth of the same specimen (fig. 3 h) has an equally slender and 

 smooth principal cusp slightly inclined backwards ; but its extended base is 

 marked Avith feeble vertical wrinkles. About five lateral denticles are shown in 

 front, but they are indistinctly divided ; and there are two acuminate lateral 

 denticles behind. An isolated tooth (fig. 4), evidently of the same species and of 

 nearly the same position in the jaw, has the anterior extension of the crown ouly 



