PLATE VII. 



Streptelasma robustum, Whiteaves (page 109). 



Figure 1 Transverse section of a specimen, from East Selkirk, Man., collected by the 

 writer in 1890. m 



Streptelasma rusticum, Billings (page 110). 



Figure 2. Side view of a specimen from Lake St. John, Que. 



Figure 2a. Longitudinal section of the same specimen. 



Figure 3. Transverse section of a stouter specimen from the same locality. 



Streptelasma caliculus, Hall (page 113). 



Figure 4. Side view of a specimen from Grimsby, Ont., showing the position of one of 



the alar septa. 

 Figure 4a. Longitudinal section of the same. 

 Figure 46. Transverse section of the same. 

 Figure 4c. Another view of the same specimen to show the surface markings indicating 



the position of the cardinal septum. 



Streptelasma rectum, Hall (page 117). 

 Figure 5. Transverse section of a specimen from the Mackenzie River. 



Zaphrentis affinis, Billings (page 118). 



Figure 6. Side view of one of the type specimens, from Wreck Point, Anticosti. 

 Figure 6a. Longitudinal section of the same. 

 Figure 66. Transverse section of the same. 



Zaphrentis Minas, Dawson (page 128). 



Figure 7. Side view of one of the types from West River, Pictou, N.S. 

 Figure 7a. Longitudinal section of the same. 

 Figure 76. Transverse section of the same. 



