206 MULTI VALVES. 



they are all more or less of a conical form, com- 

 posed of several valves, and are parasitical. The 

 animals inhabiting them are very similar, and 

 differ much from other mollusks. They have no 

 head or eyes, the mouth has jaws, with horny 

 laminae or erect teeth ; hut the most singular part 

 of their structure consists in the numerous tenta- 

 cular, curled, articulated arms ; these vary in num- 

 ber, some of the species have as many as twenty- 

 four. They are arranged in pairs, and are all in- 

 serted together ; the twelve longest are erect 

 and arched, appearing like curled feathers ; they 

 are clear and horny ; each joint is furnished with 

 two rows of hair on the concave side. The ani- 

 mals make use of these organs to catch their prey, 

 and are continually extending and contracting 

 them. The twelve smallest are placed in front, 

 they are more flexible, and more thickly set with 

 hairs than the others. 



The sessile shells * are now formed into a dis- 

 tinct genus called Balanus : they adhere imme- 

 diately to marine substances at their base, and 

 remain immoveably fixed for life ; the form of the 

 shell is conical, and the valves of which it is com- 

 posed, are so strongly cemented as almost to ap- 

 pear like a single piece. From the construction 

 of the shell, its immoveable walls, and its large 

 opening at the apex, the animal would be in a 

 very exposed and perilous situation, had not the 

 compensatory providence of the Creator been ex- 

 * Plate X. figure 6. 



