i 5 6 



HARDWICKE'S SCIENCE-GOSSIP. 



straight spine is imbedded in the muscular tissues at 

 the back of the head. The structure of the paired 

 fins, so far as can be ascertained, is singular, and 

 there is a long dorsal fin behind the spine, but the 

 caudal is imperfectly known. The skin appears to 

 have been almost destitute of shagreen, and hence 

 traces of the internal skeleton are well shown ; 

 there is evidence of the notochord being persistent, 

 but neural and haemal arches, with interspinous 

 elements for the support of the dorsal fin, are 

 distinctly visible. 



known by Sir Richard Owen in his " Odontography," 

 in 1840. The crown of the tooth is somewhat petal- 

 shaped — a peculiarity suggesting its name — and is 

 fixed upon a remarkably long root ; the cutting edge 

 is slightly denticulated, and a number of transverse 

 folds of enamel usually appear at the base. It is 

 essentially a laniary tooth, and no part can have 

 been used for grinding or crushing ; but the mode 

 of arrangement of the dentition in the mouth, and 

 the number of its components, can only be inferred 

 from what is known of allied forms, no very perfect 



Fig. 101. — Upper anterior 

 tooth of I'alcrospinax 

 prisons. 



Fig. 102. — Lower anterior 

 tooth of Palceospinax 



prisons. 



Fig. 103. — Anterior tooth of 

 Drep mephorus canalicu- 

 latus. 



Fig. 104. — Posterior tooth of 

 Drepancpliorus canahcu- 

 latus. 



LM 



A b 



Fig. 105. — Dorsal spines of Pal&ospinax priscus. 



Fig. 106. — Dorsal spines of Drepaucphorus canaliculars. 



Fig. 107. — Spine of Pleuracanthus lavissimus (i nat. size). 



' 



o 



Fig. 10S. — Trans 

 sect, of spine of 

 Orthacanthus. 



Fig. 109. — Tran?. 

 sect, i f s-pine of 

 Pleuracanthus 

 lavissimus. 



Fig. no. —Tooth named 

 Diplodus gibbosus. 



Fig. in. — Tooth of 

 Pctalodus aciuiiiiiatus. 



PETALODONTIDjE. 



Like the group just considered, the Petalodonts 

 constitute an extinct family, ranging only through a 

 limited space of geological time ; numerous genera, 

 or so-called genera, are known to occur in strata of 

 Lower Carboniferous to Upper Permian age, but 

 none appear to have been discovered in deposits of 

 later date. These fishes were evidently destitute 

 of spines, and so are represented as fossils merely by 

 teeth, shagreen, and occasional fragments of cartilage ; 

 but we are fortunate in possessing important informa- 

 tion regarding the arrangement of the dentition in at 

 least two of the forms, and these particulars afford 

 valuable aid towards determining the natural affinities 

 of the group. 



The type-genus is Pctalodus (fig. in), first made 



examples of jaws of Pctalodus itself having hitherto 

 been met with. It occurs abundantly in the Lower 

 Carboniferous, and specimens have even been re- 

 corded from the Coal Measures, but, as will presently 

 be shown, the identification of the latter must be 

 regarded as doubtful. 



(7o be continued.) 



On June 9th a statue of Mr. Darwin, executed by 

 Mr. Boehm, R.A., was unveiled in the British 

 Museum of Natural History, South Kensington, in 

 presence of the Prince of Wales and a large assembly. 

 Professor Huxley, as Chairman of the Memorial 

 Committee, made over the statue to the Prince of 

 Wales, who represented the Trustees of the British 

 Museum. 



