1880.] NATURAL SCIENCES OF PHILADELPHIA. 49 



transverse diameter of the pedal ganglion, rather strong. The buccal 

 ganglia of roundish form, connected through a very short commissure ; 

 the gastro-tiesophageal ganglia short-stalked, reaching scarcely one- 

 quarter of the size of the former, with one very large and some 

 smaller cells.' 



The eyes with black pigment and shining, horn-yellow lens. The 

 otocysts at the slight emargination at the outer margin of the cerebro- 

 visceral ganglia, crammed with otokonia of the usual kind. The broad 

 leaves of the rhinophoria stiffened in the usual way by long, much 

 calcified spicula, perpendicular on the free margin of the leaves. The 

 skin of the back crowded with spicula,^ mostly very large and much 

 calcified; in the rather low (height 0.5 mm.) granules (fig. 2) crowded 

 erect spicules. In the interstitial tissue of the intestines true spicula 

 are neither many nor large. 



The mouth-tube about 2.0 mm. long, strong, rather wide, quite as 

 usual. The bulbus pharyngeus .3.0 mm. long, with a height of 2.8 

 and reaching a breadth of 2.5 mm. ; the rasp-sheath also projecting 

 1.0 mm. from the hindermost part of the under side of the bullus. The 

 form of the bulbus and its retractors as usual ; the lip-disk whitish, 

 clothed with a yellowish cuticula. The tongue of usual form ; on the 

 shining horny-yellow radula eleven rows of teeth, further backwards 

 twelve developed and four younger rows ; the total number of rows 

 thus twenty-seven. 3 The teeth of yellowish color ; the height of the 

 outermost 0.06, of the next 0.08 mm. ; the height reaches at most 

 about 0.22 mm. The two foremost rows were rather incomplete, in 

 the fourth row were twenty-four, and the number of teeth then in- 

 creases to twenty-seven.^ The rhachis (fig. 3a) rather broad. The 

 plates of the usual form,^ with the usual wing-like expansion of the 

 exterior part of the body and of the root of the hook (figs. 4, 5) ; the 

 first (fig. 3) with lower hook, which on the succeeding teeth slowly 



1 This representation of the central nervous system in most points agrees 

 with that of Hancock and Embleton (1. c. p. 233, PI. XVII, tig. 2, 3). 



2 Collingwood (Annals and Mag. of N. Hist., 3 Ser., Ill, IS^jQ, p. 462) 

 mentions the spicules of this species (from the estuary of the Mersey) as 

 "very elegant, consisting of a broad embossed ph\te with a double and 

 beautifully serrated edge, tei'minating abruiitly in a blunt apex." 



" Alder and Hancock mention twenty-four rows, whereof eleven were on 

 the tongue. 



■• Alder and Hancock mention twenty-five plates in the rows. 



^ Cf. my Malacolog. Unters. (Semper, Philipp. II, ii), Heft XIV., 1878, 

 (Asteronotus), p. 036. 



