1905.] NATURAL SCIENCES OF PHILADELPHIA. 675 



While not plentiful, it presented itself in a number of gatherings con- 

 taining also T. volvocina, hispida and piscatoris. 



This same species has also been collected in Iowa by Prof. C. H. 

 Edmundson, who has kindly sent specimens for identification and 

 comparison with Eastern forms. 



Explanation of Plate XLI, 



Fig. 1 . — Trachelomonas crebea, a prevalent form, not typical 



Fig. 2. — Trachelomonas verrucosa. , 



Fig. 3. — Trachelomonas obtusa. 



Fig. 4. — Trachelomonas Stokesiana, front view. 



Fig. 5. — Trachelomonas Stokesiana, side view. 



Fig. 6. — Trachelomonas horrida. 



Fig. 7. — Trachelomonas rugulosa, front view. 



Fig. 8. — Trachelomonas rugulosa, side view. 



Fig. 9. — Trachelomonas armata, posterior spines undeveloped. 



Fig. 10. — Trachelomonas armata, posterior spines partially developed. 



Fig. 11. — Trachelomonas armata, posterior spines developed. 



