14 Henrij Basseii, Jan. — Projja ration of Sp/ierulites. 



of the pygidial pleuree. On the other hand, Pr. Byclcliolti (Barr.),^ to 

 which Salter saw a resemblance, agrees in the shape of its head- 

 shield, in the faintness of the lateral furrows of the glabella, in the 

 size of the genal spines ; in the median tubercle on the occipital ring ; 

 in the relative size of the eyes ; and in the general aspect of the 

 pygidium. But it differs in the shape and proportions of the glabella 

 and of the thorax ; in the absence of lateral occipital nodules ; in 

 the shape of the pleuree ; in the more rapidly tapering axis of the 

 pygidium ; and in the smooth test. Pr. Fletclieri shows, thei'efore, 

 a much closer resemblance to Pr. hohemicits than to Pr. Byckholti. 



EXPLAXATIOX OF PLATE I. 

 'Fig. 1. — L'tchas scutaUs. Salter's origiual specimen, a 954 ; Weulock Limestone, 



Malvern, x IJ. 

 Fig. 2. — Lichas scutalis." Fletcher Collection siiecimeu ; Wenlock Limestone, 



Malvern, x 1^. 

 Fig. 3. — Lichas scutalis. Hypostome of Fletcher Collection specimen, x 2. 

 Fig. 4. — Lichas scutalis. Outline restoration, x 2k. 

 Fig. 5. — Proetus Flctcheri. Salter's specimen, a 825 ; "Wenlock Limestone, Dudley. 



X 2. 

 Fig. 6. — Proetus Flctcheri. Side view of same specimen. 



XoTE. — The two figured specimens of Lichas scutalis are bent up at the head and 

 tail, causing some foreshortening of these parts in the figures, and the ends of the 

 ■pleuTce to be widely separated. 



IV. — Note on the Preparation of Spherulites. 

 By IIexry Bassett, Jun. 



LAST February, while working in the Chemical Laboratory of 

 University College, London, I had occasion to make some 

 •sulphanilic acid. This was done in the usual way by heating a mixture 

 of 100 grammes of concentrated sulphuric acid and 30 grammes of 

 aniline to 180°-190° C. in an oil bath for four hours. The flask 

 containing the mixture was left in the oil bath to cool, and on 

 examining it the next day I was surprised to find that the solid mass 

 inside had developed a beautiful spherulitic structure. As I believe 

 this has never been observed before, it may be Avorth a description. 



In colour the material is a bluish (or sometimes greenish) grey, 

 and it is practically a mass of spherulites, some of which are an 

 inch in diameter. They are mostly well developed, and are slightly- 

 lighter in tint than any intervening portions of the mass in which 

 a spherulitic structure is only faintly visible. They consist of 

 concentric layers, alternately nearly white and pale blue in colour, 

 with rather ragged edges, as may be seen in the figure. Adjacent 

 spherulites, or sometimes even what are apparently simple ones, 

 often exhibit sharp divisional planes like joints, from the one having 

 grown up against another as they were developing from independent 

 centres. Though these centres cannot in all cases be seen, there is 

 ■sufficient evidence in others to justify applying this explanation to 

 all. The mass, judging from the position of the spherulites, seems 

 to have started crystallizing from a number of independent points, 

 both on the surface of the glass and on the surface of the molten 

 mixture. 



1 Barrande : Syst. Silur. Bohem., vol. i (1852), p. 439, pi. xv, figs. 15-19. 



I 



