r-^ymoxd: notes ox the ontogeny of paradoxides. 235 



in the youngest stages knoAvn, becomes proportionately shorter (hiring 

 some of the early nepionic stages (pusillvs stages), and becomes longer 

 again in the neanic and early ephebic stages. The palpebral lobes are 

 in general very much longer in young stages than in later ones, but 

 many species are primitive in this regard, and retain the long eyes at 

 maturity (P. rugulosius group). Most of the adult characteristics are 

 assumed at an early age, so that specimens 6-10 mm. long are often 

 almost identical in form with the adult; but certain minor features 

 such as the lateral extention of the second thoracic segment, persist 

 well on into the ephebic stages. 



ApjjUcaiion to P. harlani. It will now be seen why the form of the 

 brim of this species is so important. The wide brim is a feature 

 Avhich, in this genus, is decidedly larval in character, and in such forms 

 as are knowTi to have had it, it is lost at an early age, when the cepha- 

 lon was 6-10 mm. long. Its retention in large adults like P. harlani 

 is most unusual. Another result arrived at above is applicable to 

 P. harlani. It was found that the glabellar furrows were not lost by 

 the adult, but that, on the contrary, the adult had more furrows than 

 the young. None of the very young of P. harlani are known, but the 

 smallest glabellas now before us (11 mm. long) show two pairs of 

 furrows which cross the glabella and another pair, (Xo. 2), which are 

 faintly indicated at the sides. The small cranidium figured (Plate, 

 fig. 3) which is 19 mm. long, shows a similar condition, but the No. 2 

 furrows are much more distinct. In some of the largest specimens 

 (glabella 100 mm. long) furrows 1 and 2 are both distinct, and most 

 specimens with cranidia more than 40 mm. long show all four pairs of 

 furrows. In these two features, then, the wide brim and the slow ac- 

 quisition of glabellar furrows this species is very primitive. 



The palpebral lobes in the smallest specimen mentioned above 

 reach from the glabella back to the occipital furrow, and their chord 

 is 6 mm. in length. In specimen No. 22 they meet the glabella, but 

 terminate 1 mm. in front of the occipital furrow, and the chord of the 

 lobe is 7 mm. In the adult this eye is proportionately much smaller, 

 for, on a cranidium 79 mm. long the posterior end of the lobe is 9 mm. 

 from the occipital furrow and 8 mm. from the glabella, the chord of 

 the lobe being 21 mm. Thus the proportion of the length of the chord 

 of the palpebral lobe to the length of the cranidium in the smallest 

 specimen is .50, in the second, .32, and in the adult, .26, or a reduction 

 of about one half. In common with most other species of Paradoxides, 

 P. harlani shows a great lateral extension of the fixed cheeks during 

 the process of growth. 



