15 281 



length * and larger ones from 170 to 385 mm., but in the largest specimens examined, 

 surpassing 708 mm. in length. In F. tabacaria onlj' the small and middle-sized specimens 

 up to about 400 mm. in length show minute asperities of the same kind as in the former 

 species. The smallest specimen at my disposal is figured on PI. VII, fig. 1. It has a 

 length of 43 mm.; the caudal filament exceeds the body, being about 52 mm. Most 

 of the body is covered with proportionately large, hooked spineJets, only a longitu- 

 dinal strip along the middle of each side, the head and the adjoining part of the 

 body, being naked. The spinelets appearing on the crests of the head and on the 

 nape are denticulations belonging to the deeper skeletal parts mentioned below. A 

 much larger specimen (280 mm.) shows still a general coating with small asperities, 

 most densely developed on the tail; but in two specimens of about 400 mm. the 

 dorsal part of the body is to a great extent naked, whereas the lateral and ven- 

 tral parts have their rugosity well developed. On the other side a third specimen, 

 c. 350 mm., at first sight seems completely naked; but examined with a strong lens 

 the tail ventrally to the lateral line shows very small asperities. In large specimens, 

 exceeding 700 mm., I have not been able to detect any booklets at all. Thus F. ta- 

 bacaria in the fully adult state seems to be naked. The same is probably the case 

 always with F. depressa, even in the youngest stages; but quite small specimens I 

 have never seen. The six specimens examined by me, from 250 to 450 mm. in 

 length, at all events show no trace whatever of asperities. 



The spinelets in F. tabacaria and F. petimba are of the same type: a coni- 

 cal, sharply pointed hook, basally hollow and expanded into an extremely thin 

 cup-shaped plate, generally with irregularly indented margins. In large specimens 

 of F. petimba many of the asperities appear conical or blunt, having lost their 

 hooked point, which has either been absorbed or worn away'. 



The dimensions of the asperities in some of the specimens examined are the fol- 

 lowing : 



Fist ularia petimba Diam. of basal plate Height of spine Diam.of spine at base 



A. c. 720 mm. 0,160 x 0,176 — 0,240 x 0,288 



B. C. 710 — 0,160 X 0,176 



C. c. 340 — 0,160 X 0,176 

 Fistularia tabacaria 



A. C. 400 — 0,080X0,088 — 0,128X0,136 



B. c. 350 — 



C. c. 280 — 0,096 X 0,112 



D. C. 43 — 0,080; — 0,208 



II. In Fistularia tabacaria longitudinal rows of short spindle-shaped ossicles (of 

 4 — 8 mm. length in adult specimens), imbedded in the deeper layer of the cutis, 



* The length in all cases mentioned is measured from the tip of the snout to the base of the 

 caudal filament. 



