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Genus 2. SPIRULA, Lamarck. 



Animal ; body contained in an oblong mantle, entirely free at the 

 opening, and terminating at the edge in three short festooned 

 processes, two behind, between which the funnel protrudes, and 

 one in front ; lower half of the mantle enclosing a tubular shell 

 convoluting over towards the front, with the narrow portion at 

 the bach ; base of the mantle furnished underneath with a dark 

 leathery gland, having a round cavity or orifice in the centre 

 and a short semicircular fin on either side ; head prominently 

 rising out of the opening of the mantle, entirely free from it, 

 crowned with eight short acuminated arms and two rather long 

 tentacles; arms promiscuously furnished on the inner surface 

 icitli minute granular suckers; tentacles terminated by a small 

 rounded indented club. 



Shell ; a thin transparent diminishing tube convoluted into a dis- 

 coid spire of which the lohorls are not contiguous, and partitioned 

 into chambers by concave septa, with a continuous siphon passing 

 through the inner side. 



The history of the Spirilla is one of especial interest from the circum- 

 stance of its shell, as in the case of the Nautilus, having been collected 

 in great abundance long antecedent to any discovery of the soft parts. 

 The shell was figured during the latter part of the seventeenth century by 

 our countryman Lister, but we find no vestiges of the animal until the 

 appearance in Paris of a somewhat mutilated specimen, collected by an 

 eminent French voyager, M. Peron. In M. Peron's example of the Spirula 

 the tentacles were broken off to about the length of the surrounding arms, 

 but it was sufficiently perfect in other respects to assist Lamarck in estab- 

 lishing the ceplialopodic relation which the chambered construction of its 

 shell had suggested with the Nautilus. An important difference, however, 

 presented itself in the relative position of the animal and its shell as com- 

 pared with the Nautilus. Instead of the lower portion of the body being 

 capable of fitting into an aperture or outer chamber, as Rumphius' figure 

 of the Nautilus indicated by its size and the appearance of a ligament 

 fitting to the siphonic tube, it was found to contain the shell, or chief 

 portion of it, within, — a decapodous Cephalopod having the well-known 

 little spiral shell enflanked within the lower part of the mantle. No other 

 example of the Spirula presented itself for upwards of thirty years, when a 



