SUBPHYLUM B. UROCHORDATA (TUNICATA).
- Group Larvacea and others.
SUBPHYLUM C. CEPHALOCHORDATA.
- Amphioxus—lancelet.
Note. In this chapter all the generic names printed in italics are those of extinct animals.
SUBPHYLUM D. VERTEBRATA.
DIVISION (I). CYCLOSTOMATA.
- Order 1. Marsipobranchii.
- Family Myxinoidei. Myxine—hag-fish.
- Bdellostoma.
- Family Petromyzontidae. Petromyzon—lamprey.
- (Ammocoetes—larval lamprey.)
- Family Palaeospondylidae. Palaeospondylus.
- Order 2. Ostracodermi.
- Suborder 1. Heterostraci.
- Family Pteraspidae. Pteraspis.
- Suborder 2. Osteostraci.
- Family Cephalaspidae. Cephalaspis.
- Suborder 3. Antiarcha.
- Family Asterolepidae. Pterichthys.
- Asterolepis.
DIVISION (II). GNATHOSTOMATA.