CALIGOIDEA. 1321 



upper membrane of the buccal mass is connected with the bones of 

 the lateral margin, except a small subtriangular piece either side, near 

 the anterior angle (d, a, e, fig. p), between which pieces there is a 

 semicircular opening; the edges of this opening are furnished with 

 cilias, and constitute the lower margin of the lunar opening, or the 

 lower Up. This lower lip is divided at its centre {b, fig. lp), and the 

 edges thus formed are curved inward, so that in a vertical view 

 several cilisa are projected together, and have the appearance of one 

 branching cilia. 



The whole membrane forming the upper portion of the buccal mass 

 may be called the upper lip. It is represented separate in fig. p 3 . It 

 is united with the lower portions, at its anterior extremity (q, q, figs. 

 p and p 3 ). It may be viewed as consisting of two parts, a moveable 

 and an immoveable. The moveable portion, which is very much the 

 smallest, is an elliptical, nearly circular membrane, inserted in a semi- 

 circular concavity (a a) in the anterior margin of the immoveable por- 

 tion. Its front edge is coarsely subcrenated and furnished with ciliae. 

 The large immoveable portion of the upper lip is bounded by a bony 

 edge on all sides except between p and p. At / (figs, p and p 3 ) , there 

 is a curved process, elongated outward, serving for the attachment of 

 a muscle. 



Through the opening between the lips (fig. p), we may observe the 

 two slender bones I (fig. p 1 ), and just before these, there are visible, 

 through the membranes, two dentated organs, which, when the mem- 

 branes above are removed, appear as represented in fig. p 2 . These 

 organs are the mandibles. They are long slender organs, with a falci- 

 form termination, curved inward, and dentated on the interior edge ; 

 the number of teeth is about twelve. The outer margin of the den- 

 tated portion is provided with a narrow, corneous, transparent edge. 

 These mandibles extend backward, and pass out of the buccal mass 

 just anterior to the lateral projection, c (figs, p and p'), and behind 

 the process, /. Here they are connected with a bony tendon, to 

 which the large muscles are attached which move the mandible. The 

 mandibles have no appendages, and are very slightly connected at 

 their base with the membranes of the buccal mass. When the buccal 

 mass is separated from the body by force applied below, the mandibles 

 invariably remain attached to their muscles. 



The remaining corneous organs at the extremity of the mouth have 

 been already described as connected with the lower membrane ; the 



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