62 



Petromyzon moedax. Richardson. 



Radii:— D. 53—80; C ? 



Plate XXXVIII., figs. 3—5 natural size ; 6 magnified. 



In this lamprey the vent is one-seventh of the whole 

 length of the fish distant from the tip of the tail, and 

 the first gill-opening is at an equal distance from the end 

 of the snout. The first dorsal, short and rounded, is con- 

 siderably behind the middle of the fish, and is widely sepa- 

 rated from the second one, which is much longer and 

 passes the vent by a quarter of its length. The caudal 

 is divided into an upper and under lobe, which vanish at the 

 lip of the tail. Delicate rays support these fins, but the 

 thickness of the skin prevented me from reckoning them. 

 None exist at the extreme tip of the tail, nor in a low mem- 

 brane which connects the upper caudal lobe with the second 

 dorsal. There is also a short membrane destitute of rays 

 before the under lobe, and a pale mesial stripe extends from 

 it to the vent. The rest of the fi.sh is coloured dark umber 

 brown, paler on the belly, and there is a pale spot between 

 the eyes, behind the solitary nasal tube. 



The orifice of the mouth is a longitudinal slit, armed on 

 the edges by acute teeth set altei'uately in two rows, as re- 

 presented in figure 5. Figure 6 exhibits the inside of the 

 mouth with the lips shaved off, and shows a circle of about 

 thirty small acute teeth, with a solitary one in front. More 

 within before the oesophagus there is a horny plate on each 

 side of the mesial line, having three conical, acute cusps ; 

 and beneath the oesophagus there are five teeth ranged in 

 a transverse curve terminated at each, end by a larger tooth 

 having two acute cusps. The tongue is represented by the 

 artist as projecting forwards and nearly concealing the ori- 

 fice of the gullet, but the exact form of the two large 

 teeth on its fore edge is not well shown. Though these 

 teeth appear conical when viewed in front, they have, in 

 fact, a crescentic, serrated, cutting edge, and they are 

 inclined to each other, so as to meet on the mesial line in 

 an acute angle : behind them there is a row of small teeth 

 like a saw, on each side of the tongue, which are not shown 

 in the figure. The P. tridentifer of the Fauna Boreali- 

 Amerivana, another species from the Pacific Ocean, has 

 the teeth very difierently arranged. 



Length of the only specimen of P. mordax in the collec- 

 tion, lOj inches. 



Hab. Seas of Van Diemen's Land. 



viduals of the same species in this genus, I have not ven- 

 tured to consider them as distinct. The Clupea nastts of 

 Bloch (429, fig. I.), is a more slender fish, whose height, if 

 we may judge from the drawing, does not exceed one- 

 fourth of the total length. Cuvier considers come and na- 

 sus as the same species, and Russell on the other hand 

 refers come to the Clupea thrissa of Bloch, but we do not 

 think that either of these approximations can be supported 

 by the figures. 



This fish is greatly compressed, its thickness being little 

 more than one-fifth of its greatest height, which again 

 is equal to one-third of the length including the tips of the 

 caudal fin. The profile excluding the tail is a regular oval. 

 The belly is serrated and very acute, and the edge of the 

 shoulder from the fin to the cranial plate is also very 

 acute. The head forms about one-fifth or rather more of 

 the total length, and it has the usual cranial plate, covered 

 with smooth skin. This plate has an almost obsolete cen- 

 tral ridge, from whence it slopes very gently to each side. 

 It is bounded laterally by the orbit, and a groove running 

 backward and tenninating on the side of the occiput in six 

 or seven short fuiTows, as shown in figure 8. The nose 

 projects a little beyond the small, toothless mouth, whose 

 orifice when viewed in front is triangular, and the tip of 

 the lower jaw fits into a smooth notch in the middle of the 

 upper one. The small, slender, linear maxillary is not con- 

 cealed by the preorbitar when the mouth is closed. There 

 are about forty scales in a longitudinal row and fifteen 

 or sixteen rows in height. Faint impressions on the 

 scales, give the appearance of as many lateral lines as 

 there are rows, but there is no well-marked lateral line. 

 The exposed disks of the scales are narrow, vertical rhombs 

 with sharp angles. A detached scale is transversely oval 

 with obtuse ends, without fan-like streaks on the base, and 

 having the uncovered edge rather deeply crenated. Scaly 

 sheaths exist at the bottom of the dorsal and anal ; and 

 long scales lie over the pectoral and ventrals and also be- 

 tween the latter fins. The caudal is deeply forked, with 

 acute lobes. The ventrals are under the middle of the dor- 

 sal. The colour of the fish in spirits is silvery with a 

 bluish gray tint on the back. 



Length of specimen 4j inches. 



Hab. Western Australia. Indian Ocean. 



Tetrodon virgatus. Richardson. 

 Radii :— D. 9 : A. 10 ; C. 9 ; P. 16. 



Chatoesus come. Russell. 



Clupea thrissa, Russell, Coromand. Fishes, ii. p. 76, pi. 196. (Kome). 



Radii:— B. 4; D. 17; A. 22; C. 19|; P. 15; V. 8. 



Plate XXXVIII., figs. 7—10, natural size. 



Our specimen of this fish is rather higher in proportion 

 to its length than Russell's figure, but as in other respects 

 there is no marked discrejjancy, and the numbers of the 

 rays do not differ more than often happens among indi- 



Plate XXXIX., figs. 8—9, natural size. 



This Tetrodon seems to be nearly allied in form and 

 markings to T. Uneatus of Linnaeus and Bl. 141, but there 

 is some difference in the distribution of the stripes as well 

 as in their breadth, so that we can scarcely venture to con- 

 sider them as belonging to the same species, and their very 

 distant habitats is a further presumption against uniting 

 them. The form of this fish when distended is ovate, with- 

 out a beak, the teeth only and edges of the lips projecting 

 out of the general profile. The nasal orifices are at the ex- 

 tremities of a pair of tubes on each side, resembling bifid 



