16 W. C. M'INTOSH ON VALENCINIA ARMANDI. 



mentioned, is filled up by the great longitudinal muscular layer. The nerves lie in the 

 substance of the latter at once, whereas in the new form the nerves are placed quite out- 

 side the great longitudinal coat, and the whole region is much more complex. In a 

 large Canadian example of Carinella *, again, the nerves lie outside all the muscular 

 layers, but the complexity of the muscular system of the snout is equally wonderful. 

 The tip is formed of an interwoven series of longitudinal, vertical, and transverse 

 fibres — which lie within the circular coat, and interdigitate with certain decussating 

 fibres of the latter at its inner margin. A very symmetrical arrangement of this 

 kind occurs in the middle line at the tip in front of the proboscidian aperture. At first 

 the snout is quite filled up with these elaborate muscles, with the exception of the pro- 

 boscidian canal; then a series of vascular spaces form above the latter, and range 

 themselves on each side, while a great longitudinal muscular mass occurs inferiorly. 

 Strong vertical bands on each side of the proboscidian canal, and transverse muscles 

 below it, map out the region very effectively. Thus at the ganglia a transverse section 

 shows within the cutaneous layer the circular muscular coat, with it decussating fibres 

 dorsally and ventrally. The great longitudinal coat forms a complete circuit, pierced 

 here and there by the vertical and other fibres. There are apparently two great vascular 

 channels above the great transverse muscular band on each side of the proboscidian canal ; 

 but tbe septa may only indicate temporary division of a single channel. Another large 

 canal lies in the centre below the transverse band ; but the occurrence of the mouth soon 

 obliterates the latter. It is probable that all the canals communicate (as in the Anopla), 

 and the circulating medium is represented in the preparations by a minutely granular 

 substance. 



The occurrence of the special layers of separated longitudinal fibres in the new form is 

 therefore a feature of interest ; and since they are confined to the head and oesophageal 

 region of the body, it is probable they aid the animal in its progress amongst the sand. 



"Within the great longitudinal muscular layer of Valencinia Armandi is superiorly the 

 circular muscular coat of the proboscidian sheath, which divides opposite the upper part 

 of the nerve-trunks (fig. 5, os), and sends a strong band along the ventral surface of the 

 oesophageal region of the alimentary canal. Between the latter band and the chief longi- 

 tudinal layer is the great vascular channel (v) on each side. 



The external circular muscular layer (c) shows, some distance behind the mouth, a 

 tendency to form superiorly two distinct inner bands (fig. 5, ce), extending from one 

 nerve-cord to the other ; and a little further backward the differentiation is observed all 

 round the body. The circular coat also increases in thickness ; but little further change 

 ensues in this layer in its course backward, except the alteration of its relations to the 

 nerve-trunks, which pass from its outer border into the great longitudinal layer. 



The great longitudinal muscular layer forms a continuous investment, indented by the 

 two small vascular canals (vs) superiorly, and the great vascular channels (v) inferiorly 

 on its inner side, and by the great nerve-trunks externally. As we proceed backward a 

 tendency to enlargement is noticed at the regions above and below the latter, the coat 



* Dredged by Mr. Whiteaves at various points in the Gulf of St. Lawrence. 



