SPURILLA BRAZILIANA MAC FARLAND 97 



(PI. XIX, fig. 96, pi. com.), taking its origin from the pleural 

 portion of the cerebro-pleural complex. At a point about one- 

 fourth of its length from the left side it gives ofif a moderately 

 strong, unpaired nerve, the N. genitalis (PI. XIX, fig. 96, n. g.). 

 This is described and figured by Bergh as arising from the right 

 side in Sp. neapolitana. In the Brazil species no ganglion cells 

 were found at the origin of the nerve. To these three commis- 

 sures should be added a fourth loop around the esophagus, which 

 is separated from them by some distance. This is formed by the 

 cerebro-buccal connectives and the buccal ganglia. These slender 

 connectives (PI. XIX, fig. 96, cer. hue. eon.) arise from the cere- 

 bral ganglia just below and in front of the eyes. The buccal 

 ganglia themselves are quite similar to those of the Neapolitan 

 species. They are oval in form, 0.24 mm. long by 0.21 mm. broad, 

 and are united by a very short (0.042 mm.) and broad com- 

 missure. A pair of small gastro-esophageal ganglia are closely 

 united to them. 



From the antero-dorsal portion of the cerebral ganglia arise 

 the short stout olfactory nerves (PI. XIX, fig. 96, olf. n.), which 

 dilate into the very large elliptical olfactory ganglia at the base 

 of the rhinophores. These nerves should, perhaps, be termed 

 cerebro-olfactory connectives, the name olfactory nerves being 

 reserved for the branches arising from the summit of the ganglia, 

 which are distributed to the olfactory epithelium of the rhino- 

 phores. 



The small optic ganglia, bearing the eyes (PI. XIX, fig. 96, 

 e.), lie upon the dorso-lateral margin of the cerebral ganglia, in 

 direct contact with them, and above the origin of the cerebro- 

 pedal connectives. Immediately behind these are the approx- 

 imately spherical otocysts (PI. XIX, fig. 96, at.), 0.045 ^^' ^^ 

 diameter, containing many small otoconia of an ellipsoidal shape. 

 In sections the otocysts are seen to lie upon and behind a group 

 of small ganglion cells, outside the limits of the cerebro-pleural 

 complex, and probably to be regarded as an otic ganglion, but 

 the preservation of the material precluded any decision as to 

 their exact relationships. 



Plate XIX, fig. 96 shows the origin of the nerves from the 

 central nervous system in Sp. hraziliana, being much the same 

 as that given by Trinchese for Sp. neapolitana. Nerve VII 



